Studies on the Organization and Developmentof Scorpions.

E. N. Pavlovsky, M.D., D.Sc,

Professor of Zoology in the Military Academy of Medicine, Petrograd.

With Plates 31-3.

INTRODUCTION.

IN this work I have undertaken the study of the differentorgans of scorpions from the point of view of comparativeanatomy. The extensive literature on this subject containsa number of gaps (e. g. the male genital organs have not beeninvestigated in sections), and besides in the majority of worksthe material is restricted to some species of the genera B u t h u sor E u s c o r p i u s. The necessity of studying the organizationof the tropical forms has, however, been felt for a long time.In the present investigations I had two aims in view. In thefirst place I undertook the re-examination of the structure ofsome of the most interesting organs of certain representativesof the families Buthidae, Chactidae, and Scorpionidae, on freshmaterial collected in most cases by myself in Algeria andTunis (Scorpio maurus , B u t h u s aus t ra l i s ) . Thecollection of material (Buthidae: B u t h u s caucas i cus ,A n o m a l o b u t h u s r ickmers i , L i o b u t h u s Kessler i )was continued by me in the summer of 1915 in RussianTurkestan.

The essential part of the investigations was the preparationof the scorpions from hand, the fixation of their separateorgans, and the study of the latter in sections after treatmentby modern histological methods. After having obtained reliabledata in this way, I turned to the second problem of rny work—

616 E. N. PAVLOVSKY

the study of the abundant material from the museums, whichwas placed at my disposal owing to the extreme courtesy ofa number of persons and scientific institutions both Eussian andforeign. In this connexion I consider it a pleasant duty toexpress my sincere gratitude to the Natural History Depart-ment of the British Museum, the Zoological Museum of theEussian Academy of Sciences, Museum National d'HistoireNaturelle (Paris), the Zoological Museums of Antwerp, Berlin,Calcutta, Copenhagen, Queensland, and Ltibeck.

Owing to the extreme porosity of the chitin, the interiororgans of animals kept in alcohol were preserved in such asatisfactory condition that I was able not only to dissect themuseum specimens of scorpions, but even to embed theprepared organs in paraffin and to stain them in sections.I convinced myself repeatedly that in such organs it waspossible to distinguish the tissues, which is quite sufficient fora comparative anatomical investigation. It is to be rememberedthat a standard for comparison with such necessarily imperfectpreparations was afforded by preparations from freshly fixedorgans of certain representatives of the families Buthidae,Ohactidae, and Scorpionidae.

The method of preparation of the scorpions requires specialmention. In this procedure a binocular microscope •with theupper illumination of the object is invaluable. The fresh•scorpions were dissected in 0-75 per cent, solution of commonsalt, and the alcoholic specimens in weak alcohol (50 per cent.).It may also be more convenient to dissect fresh scorpions inthe latter medium, provided it does not hinder the ultimateaims of the investigation, as in this medium the liver does notproduce any turbidity, when pieces of tissue are torn from it.Apart from pursuing the morphological aims I endeavouredin my work to obtain facts which would be of use to systema-ticists who are continually pointing out the importance of thestudy of the comparative anatomy of scorpions for theirpurposes. This idea is very well expressed in the followingwords of our arachnologist, A. A. Birula (1919, p. 54) : ' Atpresent, however, the further study of the external structure

STUDIES ON SCORPIONS 617

does not allow of grouping the genera of scorpions into morenatural sub-families. It is necessary, therefore, to "wait fora detailed comparative anatomical study of them in the hopethat the interior structure will point out new ways for ourphylogenetic generalizations.'

I have carried out a comparative study of the structureof the different organs of scorpions with the view of renderingpossible such an anatomical foundation of the classificationof these animals, and have arrived at the conclusion that themost important parts in this respect are the genital organs.I have not utilized to the full extent all the material at mydisposal, and am therefore publishing only such facts as havebeen conclusively established up to the present. The investiga-tions are still in progress and will be continued in the future,if the circumstances connected with the present unsettledconditions of life in Eussia offer no hindrance.

I have investigated to a greater or less degree the structureof the scorpions contained in the following list.

FAM. BUTHIDAB.

Lychas t r i ca r ina tus (Poc.), L. mucronatus (¥.).L. var ia tus (Thor.), L. marmoreus (O.L.Koch).

Isometrus maculatus (Geer).Centrurus elegans (Thorell), C. margar i ta tus (G-erv.).Tityus cambridgei (Poc), T. bolivianus (Krpln.),

T. sp.Buthus aust ra l is (L.), B. crassicauda (01.), B.

acutecar ina tus (E. Sim.), B. sauleyi (E. Sim.),B. judaicus (E. Sim.), B. ho t t en to t a (F.), B.eupeus (C. L. Koch), B. caucasicus (Nordm.), B.occitanus (Amor.), B. quinques t r ia tus (H. E.),B. emini (Poc).

Parabuthus planicauda (Pocock), P. liosoma (H. E.).Grosphus madagascariensis (Gerv.).Babycurus bii t tneri (Karsch.).Liobuthus Kessleri (Bir.).Anomalobuthus rickmersi (Krpl.).Uroplectes t r iangulifer (Thor.), U. l ineatus (C. L.

Koch), XL fischeri (Karsch.), U. formosus (Poc).Orthochirus scrobiculosus (Grube).

618 E. N. PAVLOVSKY

PAM. CHAERILIDAE.Chaerilus var iegatus (E. Sim.).Calchas nordmanni (Bir.).

FAM. CHACTIDAE.Broteas granimanus (Poc).Broteochactas gollmeri (Karsch.).Teu thraus tes wi t t i (Krpl.).Euscorpius i ta l icus (Hbst.), E. f lavicaudis (Geer),

E. carpa th icus (L.).

PAM. BOTHKIURIDAE.

Bothr iu rus v i t t a t u s (G.).Brach is tos te rnus intermedius, Br. ehrenbergi i

(Gerv.).Thestylus glasioui (Bertk.).

PAM. VEJOVIDAE.

Vejovis cr is t imanus (Poc). V. spinigerus (H. C.Wood).

Uroctonus mordax (Thor.).Hadrurus h i r su tus (H. C. Wood).Scorpiops montanus (Karsch.), Sc. leptochirus

(Poc).Jurus dufoureius (Brulle).Caraboctonus keyserl ingi (Poc).Hadruroides leopardus . . ., H. luna tus (L. Koch).

PAM. SCORPIONIDAE.Hadogenes ,sp .Opis thacan thus elatus (Gerv.).Opis thocent rus madagascar iensis (Krpln.), 0. le-

comt ei (H. Luc).Hormurus aus t ra las iae (P.).Jomachus pol i tus (Poc).Hemiscorpius lep turus (Ptrs.).Urodacus manicatus .Scorpio rnaurus (L.).Opis thoph tha lmus wahlbergi (Thor.), 0. ca r ina tus

(Ptrs.).Pandinus impera tor (C.L.Koch), P. exi t ia l is (Poc).,

P. peeli.He te romet rus longimanus (Hbst.), H. cyaneus

(C. L. Koch).

STUDIES ON SCORPIONS 6 1 9

1. ON THE EXTERNAL MORPHOLOGY OF THE SCORPIONS.

The questions bearing on the external morphology of thescorpions have frequently been the subject of investigationsboth by systematicists and embryologists. I shall dwell onsuch facts as were established or developed in one or anotherdegree by myself.

In Sco rp io m a u r u s I have discovered an inserted sternitelying anteriorly to the first preabdominal sternite (PI. 31.fig. 2, snx). This structure has no essential morphologicalsignificance, since it evidently represents a derivative of themetasternum (PI. 31, fig. 1, M, sny). For such pseudosternitesI propose the name of s t e r n o i d s . It is, however, opportuneto mark these structures, since they simulate the true sternitein some individuals of S. m a u r u s . It is also necessary todraw attention to the same names given in the literature todifferent other structures. Taking as a starting-point thestructure of the sternum in the fossil S t e r n a t h r o n , Burner(1902) believes that the primitive sternum consisted of thepro-, deuto-, trito-, tetra-, penta-, and meta-sternum, whereasalready previously to Borner's works the term metasternumwas used to signify the basal plate of the pectines in scorpions.On account of this it is desirable to substitute for metasternumin Borner's sense some other name, e.g. o p i s t h o s t e r n u m .In one of my preceding papers (Pavlovsky, 1916) I havedemonstrated in figures that the normal correlation betweenthe length of the post-abdomen and cephalothorax is estab-lished in B u t h u s e u p e u s and H e t e r o m e t r u s onlyafter the firat moult of the new-born scorpion. On the otherhand, as is shown by my observations, in scorpions withspecially long tails (Cen t ru rus ) one moult is not sufficientfor the establishment of the normal correlation of the lengthof the cephalothorax and the tail. Besides, in young scorpionsthe males and females begin to differ in the proportions ofthe named parts in connexion with the appearance of sexualdimorphism (Table I).

620 K. N. PAVLOVSKY

TABLE I,

Centrums margari tatus.

Xos.

1. New-born scorpions2-3. "iPulli after the first4. j moult5. „ „6.7.8.9-

10. Adult $11.12.13.14. Adult 315.

Length ofCephalo-thorax.

mm.1-41-31-81-81-71-81-81-81-83-83-07-88-07-08-0

LengthofPre-

abdomen.

mm.4-04-03-53-63-73-83-13-631

12-810-7—

27-419-222-3

Lengthof Tail.

mm.4-54-57-77-37-28-17-87-87-9

20-014-046-050'800-762-4

Relation of theLength of

Cephalothoraxto Length of Tail

Per cent.3-23-54-34-14-24-54-34-34-35-34-76-06-358-77-8

The process of displacement of the middle eyes observedduring the growth of O p i s t h o p h t h a l m u s , according toLaurie, takes place in different degrees in other scorpions aswell, according to my observations (PL 31, fig. 6: L y c h a st r i c a r i n a t u s , L . ma r more u s , H e t e r o m e t r u s c y a -neus) .

Apart froni the anteriorly displaced arrangement of themiddle eyes, the new-born scorpion differs from the adultscorpion that has moulted once in its life in the followingcharacters. In H e t e r o m e t r u s the sternum is situatedbetween the coxae of II, III, and IV pairs of legs (PI. 31,fig. 5, st). The displacement of the sternum posteriorly, andthe assumption of its normal position between the III andIV pairs, takes place during the first moult of this scorpion(PL 31, figs. 3, 4, st).

Therefore its sternum should be considered as homologousto the tetra-penta-opisthosternum.

The legs of all new-born scorpions terminate in an acumina-

STUDIES ON SCORPIONS 621

tion through the skin of which the claws, revealed only afterthe first moult, are visible (PI. 31, fig. 14). This form of leg innew-born scorpions corresponds to the extremities of P a 1 a e o -p h o n u s which are pointed at the end.

The chelicerae of H e t e r o r n e t r u s and O p i s t h o c e n t r u sare provided with provisional appendages, already known tous, which play a role in the nutrition of the developing embryo.Contrary to Laurie's (1896) statement the cord-shaped appen-dage in O p i s t h o c e n t r u s does not bifurcate (PI. 31, fig. 7,ch). The motile branch of the chela in H o r m u r u s is alsoprovided with a provisional structure in the shape of a spineof indefinite function. In O p i s t h o c e n t r u s the tergites ofthe abdomen are. covered with provisional spinelets arrangedin groups of four in each segment (PI. 31, fig. 7). These struc-tures are all cast off at the first moult.

All these characters distinguishing the new-born scorpionfrom the scorpion after the first moult speak in favour of thepresence of a process of epigenesis in these Arachnoidea, andallow us to regard their pullus as a larva.

2. THE INTEGUMENT AND ITS PEOCESSES.

The chitin of the integument consists of the following parts :(1) a superficial cuticle (testostracum, PI. 32, figs. 1, 2, tc),(2) the middle layer (epiostracum, es), and (3) the deep lamellouslayers (hypostracum, hyp.)

The following structures represent the appendages of theintegument: (a) canals of the chitin ; (b) the external appen-dages—in the form of setae, spines, claws, &c.; and (c) differentglands.

The canal in the chitin are of two sorts : (1) in the hard partsof the integument there are fine smooth-walled canals (PI. 32,fig. 1, cst) reaching to the very surface of the chitin ; theirlumen is occupied by a protoplasmic strand with rod-shapednuclei, and sometimes also by pigment granules.

The pleura of scorpions are perforated by broader canals,the walls of which are covered with circular thickenings (PI. 32,fig. 2, cpr). The canals appear to perforate the cuticle of

622 E. N. PAVLOVSKY

thG chitin ; from their apices short chitinous tubules runinwards.

The sculptural derivatives of the integument are representedby (1) d e r m a t i d i a and (2) c o e l o d e r m i d i a . The formerare formed only at the expense of the dermal lining (chitin,hypoderm, m. basilaris), the latter are provided with an innercavity, representing the continuation of the body-cavity.

To the coelodermidia are referred the different diverticulaof the integument, e. g. the cristae tarsal claws, spines of theclaws, spurs, and many other structures.

The dermatidia can develop only at the expense of thechitin, and to this type are referred the chaetoids (denticleson chelae, sculptural processes on the posterior margin of thestigmata, and others).

A more complicated structure is presented by different hairsAvhich may be divided into two groups: dermatidiae athecatae(when the setae are attached directly to the chitinous cuticle,or in small depressions of the latter) and dermatidiae thecatae(when the base of the seta rests in an articulation pit or theca).The former include the following structures : simple setae orhairs (organs of sense in H e t e r o m e t r u s l o n g i m a n u s ,according to Scheming [1912]), scaphotrixes (organs of sound,according to Pocock, 1896) in the form of patelliform setaebent at their bases (PI. 32, figs. 3, 4, se). To the latter thefollowing are referred : (1) dermatidiae caelothecatae (witha hollow, more or less voluminous theca)—the trichobothria(PI. 32, fig. o, th, se), and (2) dermatidiae plerothecatae (witha thick-walled theca closely enveloping the base of the hair)(PI. 32, fig. 7, th, se)—the trichoeope (the stridulation organ ofPocock) and the neuroglandular hairs with a multicellularalveole at their base (PI. 32, fig. 8, an).

Of the dermal glands it is necessary to mention the presenceof simple alveolar glands in the chela of the pedipalpi, theirtibia, and in the legs, described by me in the pulli of H e t e r o -m e t r u s (PI. 32, fig. 6, gai).

The glandula plicata of B o t h r i u r u s v i t t a t u s deservesto be mentioned specially, and its structure will be described

STUDIES ON SCORPIONS 623

by me in detail. I have frequently had occasion to describethe structure of poison glands in scorpions (1912, 1914, 1917).In the poison ampulla are situated two sacciform glandsclothed in the ampullar cavity with a muscular membrane.

From the glands are given off fine efferent ducts opening atthe apex of the sting. The wall of the glands consists of tallcylindrical epithelium between the cells of which are insertedflat supporting cells. Exteriorly to the epithelium lies themembrana basilaris and a connective-tissue membrane. Thewalls of the gland are either smooth or folded. The criterionfor the morphological determination of these organs is pre-sented by the c h a r a c t e r of the folds of the glandular wall(which establishes their type) and by the d e g r e e of plication(which determines their form).

There are two types of poison glands. (I) Primitive glands(fundamental or embryonic type), and (II) complex glands(definitive type, folded glands). Type I is divided into twosubtypes : subtype 1—thin-walled, unfolded glands the epithe-lium of which is more or less alike in height throughout (PI. 31,fig. 15), and subtype 2—pseudofolded glands with an epitheliumof varying height, on account of which either diffuse or fewfalse folds are formed (form Av PI. 33, fig. 8), or the folds aremore definitely formed and are numerous (form A2).

Poison glands of type II are distinguished by the presenceof true folds in the organ, in the formation of which both the.epithelium of the wall and the membrana basilaris withthe external connective-tissue membrane of the gland takepart.

In such true folded glands the following varieties can bedistinguished :

(1) Form B—glands with few folds (with a single longitudinalfold), (2) form B—glands with a moderate number of folds(with two to four similar folds), and (3) form B2—glands withmany folds (more than four to five [PI. 31, fig. 16]).

The poison glands undergo a postembryonic developmentwhich is especially sharply expressed in the scorpions withglands belonging to type II. In new-born animals the latter

624 E. N. PAVLOVSKY

are smooth walled (type I, form A), and only in connexion withthe successive moults and the formation of folds does thegland assume forms B, Bl t and B2 in succession.

The family Buthidae is characterized by glands of type IIand forms Bx and B2. The arrangement of the scorpions ofthis family, according to the forms of their poison glands, isrepresented in diagram no. 1.

Bathus acutecarinatus

Orthochirus

CentrurinaeButhinae (partim)

In the family Chactidae only primitive organs belonging toforms A and Ax are found. The former is also observed in0 h a e r i 1 u s and C a 1 c h a s. The family Vejovidae differs inthe variety both of the types and forms of poison glands.Form A is present in Uroctonus rnordax, form Ax inScorpiops. Form A2 has not yet been observed in thisfamily. Hadruroides, Ju rus , and Hadrurus aredistinguished by the complex type of poison glands in all itsforms. The same variety in the structure of the organsdescribed is observed in the family Scorpionidae. The Ho-murinae have smooth-walled glands (form A); Opistho-centrus is characterized by form Ax of these organs', andOpisthacanthus by form A2. Hemihoplopus, Uro-dacus, and the Scorpioninae are provided with differentforms of complex glands (type II).

STUDIES ON SCORPIONS 625

In general there is a complete parallelism between the familyVejovidae and Scorpionidae with regard to the complicationin the structure of their poison glands, as shown in the com-parative table no. II.

Form of PoisonOlands.

. Form AType I : „ Atprimitive \glands. „ A,

/ Form B1

Type II : „ B,complex -glands. » B2

TABLE II.

Fam. Vejovidae.

UrootonusScorpiops, Vejovis

—.

Hadruroides leo-pardus juv.

Jurus, Caraboc-tonus

Hadruroides luna-t u s

Hadrurus hirsutus

Fam. Scorpionidae.

Subf. Hormurinae.OpisthocentrusmadagascariensisOpisthacanthus

elatus.

Hemiscorpius lep-turus.

Urodacus manica-tus.

Subf. Scorpioninae.

Hemihoplopus.

In the Bothriuridae I have established with certainty onlyforms B and B2 of poison glands. In a young Testylus form A1

was found. It is, however, necessary to examine the adultindividual of the same species in order to corroborate this factconclusively.

G l a n d u l a p l i c a t a of B o t h r i u r u s v i t t a t u s .

The males of some species of the genus B o t h r i u r u s (fam.Bothriuridae) are provided on the dorsal surface of the poisonvesicle with a scutelliform depression. In the male B . d o r -b i g n y i (Guer) such a structure is absent altogether. InB . b u r m e i s t e r i (Krpln.) the poison vesicle is providedonly with a slightly expressed cup-shaped pit (' Napfgrube '),this structure attaining full development only in o* B. v i t -t a t u s , which was investigated by me in the specimen fromthe Paris Museum.

The poison vesicle bears on its dorsal surface a distinctlymarked scutelliform depression, corresponding to which thereis a special organ situated underneath the dermal integument,

NO. 272 T t

626 E. N. PAVLOVSKY

hitherto unknown in scorpions. In transverse sections thefollowing picture is seen. The chitin of the poison vesiclecorresponding to the dorsal concavity is somewhat thickerthan on the remaining surface of the ampulla. On stainingthe museum preparation with Giemsa's stain a fine structurelesscuticle is revealed on the surface of the chitin which is hardlyvisible on the disc. Like in other parts of the body of the scor-pion, this cuticle does not stain. Underneath it lies a blue-coloured layer which is twice as thick and striated in thevertical direction. This blue layer is well marked only inthe central part of the disc, whilst at the circumference of thelatter it passes into a thinner layer of dark yellow colour under-lying the homogeneous superficial cuticle along the remainingcircumference of the poison vesicle. Both these portions ofchitin corresponding to the testostracum and epiostracum ofthe other portions of the body occupy only one-tenth of itstotal thickness, nine-tenths of which pass under the hypo-stracum and have a weakly expressed longitudinal striation.In its turn the deep portion of the chitin has a sharply expressedvertical striation due to the presence of countless numbers offilaments staining violet. Underneath the chitin, in the regionof the disc, the normally arranged layer of hypodermal cellsusually closely adjacent to the chitin and repeating the largefolds of the latter is absent.

At this point the hypoderm forms a special organ in theform of numerous longitudinal folds of the cubic epithelium(PI. 31, fig. 8, gp). These folds are lower along the circum-ference of the disc than in its central portion, the inner limitof which is parallel to the chitin of the scutelliform depression.Into the folds of the hypoderm are given off from the hypo-stracum bundles of fibrils reaching their blind ends (PI. 31,fig. 8, fl.). The epithelial portion of the organ described con-sists of sappy and much larger cells than in the remaining partsof the integument. Their rounded nuclei contain a nucleolusand a fairly granular network of chromatin. Along the surfaceof the folds directed towards the body-cavity there runs a verythin membrana basilaris, and between the folds are disposed

STUDIES ON SCORPIONS 627

various elements of connective tissue, e. g. blood-cells, lamellousconnective-tissue structures.

The structure described cannot be compared with anythinglike it in the other scorpions investigated by me. I am inclinedto regard it as a gland, on account of the glandular characterof the epithelium of the folds. If such is the case, its secretionmust penetrate through the chitin. This is facilitated by thefibrous structure of the latter. Besides, on the disc it is per-forated by canals reaching the superficial cuticle, as in the hardchitin of the other parts of the body. The function of thisgland being mysterious, I propose to name it provisionallyg l a n d u l a p l i c a t a .

Taking into consideration the connexion between thescutelliform depression of the dermal integuments of thepoison gland in the male B o t h r i u r u s v i t t a t u s and thespecial gland situated underneath it, it is to be supposed thatthe glandula plicata is an organ peculiar to males alone, sincethe poison ampulla of the females belonging to the given speciesexhibits no external peculiarities in its structure. The questionwhether in this case we are actually dealing with the pheno-menon of sexual dimorphism affecting not only the externalmorphology of the scorpion, but also its internal structure ina marked degree, should be solved by anatomical investiga-tions on the female B o t h r i u r u s .

Kraepelin (1908) discusses the sexual differences of scorpionsin a special paper, and points to the fact that these differencesare manifested in the modification of organs present in bothsexes, whereas the new formation of organs in any one sex(e.g. the flagellum of the Solpugids) does not take place. It isimportant, from this point of view, to determine whether thefemale B o t h r i u r u s v i t t a t u s possesses any rudiment ofa glandula plicata. If the results are negative, this will bethe only instance hitherto known, in which the male is furnishedwith a new gland, Avhich plays a certain role in his sexuallife.

T t 2

628 E. N. PAVLOVSKY

3. THE CIRCULATORY SYSTEM.

The anatomy of the circulatory system of scorpions has beendealt with in the works of numerous authors. In this paperI will only give a brief description of the microscopical structureof the heart and blood-vessels.

The heart has the following structure. The stroma of theorgan is formed of connective tissue (PL 32, fig. 11, end) con-nected with fibres on which the heart is suspended. In itssubstance are inserted semicircular transversely striated muscle-fibres (muscularis, PI. 32, fig. 11, em), exteriorly to which, inthe same stroma, are disposed fine longitudinal fibres withoutany traces of transverse striation (PI. 32, fig. 12, ecr). Theconnective-tissue framework of the heart represents the peri-and endo-mysium disposed in several layers on the side of thecavity of the organ. Thus the intima of the heart representsonly the perimysium clothing of the fibres of tunica rnuscu-laris, and is connected with the endomysrarn passing into theconnective tissue enveloping the longitudinal exterior fibres ofthe heart. It fully corresponds to the connective-tissue liningof the blood-vessels in the Annulata (Livanov, Zelensky).In the formation of the valves of the cardiac ostia two rows ofcircular fibres take part, and not one, as in the heart. Passingalong the edge of the valve suspended in the cardiac cavity,the intima of the latter passes into the perimysium of itsexterior surface. In the middle of the dorsal surface of theheart runs the sympathetic nerve (Police) containing nerve-cells in its mass (the autonomous centres of the heart ?PL 32, fig. 11, nzs). The arteries are given off from the ventralsurface of the heart, starting from paired metameric valvesaround which the base of the vessel swells in the form of a bulb.The valve proper has the form of a muff (PL 32, fig. 12, ea)which, although connected with the muscularis of the heart,is composed of ramifying muscle-cells (PI. 32, fig. 12, ema)anastomosing with each other, and enveloped on all sides bya connective-tissue membrane (=the stroma of the heart).The wall of the swollen base of the artery is apposed to the

STUDIES ON SCORPIONS 629

exterior portion of the heart and consists of stellate trans-versely striated (contrary to Gadsikiewicz, 1908) muscle-cellswith a perimysium around them. In the arteries of the scorpionthe same plan of structure is observed as in the heart: thestellate cells of the tunica nauscularis (PI. 32, fig. 10, ana) areinserted in the connective-tissue stroma (PI. 32, fig. 10, adv).Usually the arteries are lined within by a homogeneous non-nucleated lamella belonging to the category of border formation,according to Livanov (1914) ; the endothelium is apparentlyabsent in the arteries of the scorpion, as it is in its heart(Schneider, 1892). This corroborates the view expressed forthe first time with regard to spiders by Schirnkewitsch.

The general plan of the microscopical structure of the circula-tory system in scorpions agrees with Fernandez's (1905) viewon the organization of this system in the Coelomata in general.The cardiocoelomic apertures discovered by Schimkewitsch(1906) in the Pedipalpida, as well as the similar structures inthe Orthoptera (Kowalewsky, 1894), are homologous to thebulbiform dilatations on the base of the ventral arteries andtheir valves in scorpions.

4. THE SYSTEM OP LYMPHATIC (PHAGOCYTIC) ORGANS.

It is already an established fact in the literature that thescorpions are provided with a system of lymphatic organsconsisting either of a single supraneural lymphatic gland or ofthe same gland and two sacciform lymphoid organs—thediverticula of the cephalothoracic diaphragm. The singlelymphatic gland is referred by me to the simple type of thesystem named (PI. 31, fig. 9, nd), and the combination with thelymphoid organs to the complex type (PI. 31, fig. 13).

According to my observations, to which we shall now turn,the simple system of phagocytic organs is typical for theButhidae, in which it assumes different structures. SomeButhidae are provided with a noclula lymphatic gland, theseparate parts of which differing in size and form do not adjoinone another ( B u t h u s , O r t h o c h i r u s , A n o m a l o b u t h u s ,L i o b u t h u s , O d o n t u r u s , T i tyus ) , whilst other genera

630 E. N. PAVLOVSKY

of this family are distinguished by a band-shaped continuousgland running along the entire length of the preabdornen(Lychas , PI. 32, fig. 11, Id, Uroplectes) . These twoforms are connected by a transition presented by the case inwhich the strongly developed separate nodules of the lymphaticgland may be adjacent to each other and form a continuousorgan (Buthus a u s t r a l i s , PI. 31, fig. 10, nd) differing fromthe gland of U r o p l e c t u s or Lychas in its considerablethickness.

The complex system of phagocytic organs is typical of theChactidae, Vejovidae, Bothriuridae, and Scorpionidae (for listof genera investigated see pp. 617-18). Their lymphatic glandhas the form of a "continuous band (PL 31, figs. 12, 13, Id)which either does not reach the third nodule of the nerve-cord(e.g. Scorp io , O p i s t h a c a n t h u s , Vejovis , and others)or extends throughout the whole length of the preabdomen(Hadru rus h i r s u t u s , B o t h r i u r u s b o n a r i e n s i s ,B ro t ea s g ran imanus) . Twice I have observed thepresence of small nodules separated from the posterior end ofthe gland and situated between the third and fourth nodulesof the chain. Such forms, in my opinion, allow one to connectthe morphologically continuous lymphatic glands of theChactoids with the nodular glands of the Buthoids.

In general the lymphoid organs have the aspect of tubesvarying in form and size in the different genera (PI. 31, fig. 12,13, 1) : from short ovoid to long tu'bes. I shall begin thedescription of the latter from the Buthoids. Above the nerve-chain in B u t h u s eupeus , B . c a u c a s i c u s , B . aus -t r a l i s , and others, lies the supraneural artery, which differsfrom the similar vessel in Scorpio in its closer connexionwith the membranes of the chain. The latter split and theirseparated part is given off dorsally, forming a kind of canopystretched between the edges of the nerve-trunks of the chain(PI. 33, fig. 3, g).

The upper wall of the vessel has the typical structure asthere are muscle-cells (muscularis, PL 33, fig. 3, m) arrangedbetween its connective-tissue layers (intima and adventitia).

STUDIES ON SCORPIONS 631

As regards the ventral surface of the vessel, it consists only ofconnective tissue closely adjacent to the nerve-chain in whichmuscle elements are indiscernible. Notwithstanding this fact,the vessel described is to be regarded as an artery, and not alacuna as was asserted by Houssay (1S87).

On the dorsal surface the walls of the vessel form diverticula—pedicles—passing into the lymphatic gland. Its stroma isformed by connective-tissue trabeculae representing the con-tinuation of the intima and adventitia of the vessel; separatemuscle-cells also penetrate into the pedicles and the adjoiningparts of the gland (PI. 32, fig. 5, m). Each pedicle representsa ramifying tube the branches of which form the nodules of thelymphatic gland (PI. 33, fig. 3, nd). The latter is closedexteriorly by a membrane which is not always visible, asbetween the separate parts of the gland there is not infre-quently a connective-tissue network with blood-cells in itsnodes (PI. 33, fig. 3, cd).

The cavity of the supraneural vessel is connected by meansof the lumen of the pedicle with the lacunae of the lymphaticgland (PL 33, fig. 5, ->) which are devoid of an inner lining.The wall of the tubular ramifications is fairly thick. It consistsof the above-mentioned connective-tissue stroma (PL 33.fig. 5, str) which becomes deeply impregnated with collargolafter 1 per cent, aqueous solution of the latter is injected intoone of the extremities or directly into the abdomen of thescorpion. In such cases the stroma is marked by the accumula-tion of numerous black granules (PL 33, fig. 4, str) resistant tothe action of alcohol. The nodes of the connective-tissueframework of the gland are filled with a large number of variouscells. We may distinguish the fundamental cells (non-granularleucocytes or lymphocytes) constantly present in the gland,and other forms of blood elements which are not alwaysencountered in it! Thus many individuals contain numerousacidophil cells both in the lacunae and in the wall of the gland,as well as in the connective tissue surrounding it (PL 83,fig. 4, ca). Amongst these there are also proacidophils, ascanty number of basophils, and giant cells with large vesicular

632 E. N. PAVLOVSKY

nuclei staining feebly. The fundamental cells of the glandsometimes divide caryokinetically, which confirms the observa-tions of Cuenot and Kollmann and supports the reputation ofthe gland as a haematogenous organ. Its phagocytic rolenoted in the literature also stands beyond all doubt. I havecarried out numerous experiments with the injection of Sar-c inae , B. m e s e n t e r i c u s , and B. t ube rcu los i s ,p i s c ium; besides, in Turkestan (Julek, Petrovsky district).I injected into scorpions China-ink and other substances.I can also corroborate Cuenot's (1891) observations that theblood-cells escape through the exterior surface of the glandand fall into the body-cavity.

A similar phenomenon was observed by me in Scorpiomaurus as well. The immigration of the blood-cells into thelymphatic gland, which is so clearly demonstrated in Scorpio ,is quite a common phenomenon in B u t h u s , since the cellsare provided with a direct passage into the lacunae of thegland through the lumen of its podia which communicateswith the cavity of the supraneural vessel.

In general the lymphatic gland of Buthidae represents aderivative of the perimysium rnuscularis of the vessel named,which forms dorsal diverticula on its walls, in the nodes ofthe stroma of which are deposited the blood-cells undergoingmultiplication there.

With regard to the lymphoid organs of B u t h u s theliterary data are contradictory. Kowalewsky (1897) describesin the late stage of development of the embryo and in new-bornB. (Prionurus) c ra s s i cauda rudimentary diverticula ofthe diaphragm, absent in the adult scorpions, which he regardsas the rudiments of the lymphoid organs. Buxton (1913),however, followed the development of B. o c c i t a n u s , butfound no traces of any such structures. According to myobservations not one adult Buthid is provided with lymphoidorgans. In new-born scorpions, B. eupeus , B. caucas i -cus, L iobu thus , Lychas , and C e n t r u r u s , they arealso absent. Owing to the kindness of the late ProfessorW. M. Schimkewitsch, I had the opportunity of examining

STUDIES ON SCORPIONS 633

preparations of embryos of B . ( P r i o n u r u s ) c r a s s i c a u d aleft from the work of Birula. Prom one of these prepara-tions were drawn figs. 6 and 7 of PI. 33. Pig. 7 correspondsclosely enough to fig. 22, PL 32, of Kowalewsky's work (1S97);nevertheless, I cannot agree with the conclusion of the latterthat the thin-walled sacs (PI. 33, fig. 7, svlo) opening intothe diaphragm represent rudiments of the lymphoid organs.The examination of a series of horizontal sections through themature embryo shows that the sacciform diverticula of thediaphragm are in direct connexion with the ventral pulmonarysinuses (PI. 33, fig. 6, svl). Once such a correlation is estab-lished all grounds for regarding the anterior portions of thesinuses—simulating independent formations in horizontal sec-tion—as rudiments of the lymphoid organs disappear. Theirabsence in Buthidae and the special structure of the lymphaticgland serves to distinguish the Buthoids sharply from all theother scorpions investigated by me, which are provided withcomplex phagocytic organs, to the examination of which weshall now turn. As an example a description of the structureof the lymphatic gland in S c o r p i o m a u r u s (Pavlovsky,1916 b) will be given. Similarly to the Chactoids the supra-neural vessel is not so closely connected with the membranesof the nerve-chain, as is characteristic of the Buthoids. Thelymphatic gland itself (str of the same figure), however, isfused with the wall of the vessel throughout its entire length.The vessel has the structure of a typical artery, differing fromthe latter only in the absence of an interior continuous liningdevoid of nuclei. Its intima is frequently split and is probablyprovided with slits, since the plasma and blood-cells penetratebetween its layers ; neither the Scorpionidae nor Chactidaeare provided with such apertures that serve the special purposeof uniting the cavity of the vessel with the lymphatic gland,and are characteristic of the Buthidae. The media of thevessel consists of appendiculate striated muscle-cells the peri-mysium of which forms exteriorly the adventitia transformedon the dorsal and lateral surfaces of the supraneural vesselinto the stroma of the lymphatic gland. In very many scor-

634 E. N. PAVLOVSKY

pions the latter covers the parts of the vessel named in theform of a thick layer (Scorpio, Jomachus , Euscorp ius ,Vejovis , Uroc tonus , H a d r u r u s , B o t h r i u r u s , andothers). Scorpio ind icus is an exception, as its glandembraces the supraneural vessel from all sides in the form ofa muff. The trabeculae by the stroma of the lymphatic gland(PI. 32, fig. 9, stz) stain well in a blue colour, after Mallory;in their depth are deposited polymorphous elongated nucleiwith compact masses of chromatin.

In the nodes of the stroma, as in the Buthoids, are depositednon-granular leucocytes staining with Ehrlich's triacide in agreyish-crimson colour, and with Giemsa's stain in a pinkishcolour. Their nuclei are large, polymorphous, with a greatnumber of chromatin granules. In some individuals thelymphatic gland contains only these fundamental cells. Fre-quently among them are encountered, singly or in groups,basophils, proacidophils, and acidophils. The granular leuco-cytes are capable of migrating into the gland from the supra-neural vessel. Together with the immigration of the bloodelements there also takes place their emigration from thelymphatic gland. The cells rupture its exterior membraneand fall into the body-cavity. In general the lymphatic glandof the Scorpionidae and Chactidae differs from the same organin Buthidae in that its stroma is formed only at the expenseof the adventitia of the supraneural vessel and in the commonclose connexion between the gland and the supraneural vessel,which in its turn is separated from the connective-tissue mem-branes of the supraneural chain.

The structure of the lymphoid organs of Scorpio m a u r u sis most easily observed from the orifice, at the circumference ofwhich the perirnysium of the diaphragm between the cephalo-thorax and the preabdomen passes into the wall of the organ ;its stroma is formed by rather thick trabecula limiting the innercavity (PI. 33, fig. 2, in) united with the cephalothoraciccavity. In the inner part of the wall of the lymphoid organthe trabeculae have the form of cylindrical strands with ovalnuclei. In their protoplasm are deposited numerous fibrils

STUDIES ON SCORPIONS 635

(PI. 33, fig. 2, /) staining blue after Mallory. Exteriorly thetrabeculae fuse with each other, their fibrils forming what couldbe termed the spongy part of the organ which in general repre-sents a syncytium. Both in its cavity and in the depth of itswall are usually encountered blood-cells crawling amongst thetrabeculae and in the wall of the organ, where they may bedecomposed and broken up during degeneration. In the con-ditions of my experiments (1916) it was found that the lymphoidorgan takes part in the phagocytic processes. Its work,however, is not as regular as that of the lymphatic gland.

The question arises : which type of lymphoido-phagocyticorgans should be considered more primitive ? Kowalewsky(1897) considered the lymphoid sacs of the scorpions to behomologous to the sac of the septum in certain annulateworms. In this respect the lymphoid organs can be regardedas possessing an ancestral character and their presence in thisscorpion—as a primitive feature.

On comparing the lymphatic glands in the Buthidae, on onehand, with those in the Chactidae and Scorpionidae, on theother hand, it is seen that the greater complexity of histologicalstructure is observed in the former, as their supraneural vesselis united with the lymph-nodes, lying singly or in a continuousband, by special orifices.

The supraneural vessel itself is weakly developed, beingindistinctly separable from the membrane of the nerve-chain.In the Chactidae and Scorpionidae the lymphatic gland has theexternal aspect of a more perfect organ, since it always presentsa continuous band, and as such can be totally separated fromthe nerve-chain, which it is impossible to do with the sameorgans in Buthoids. Its microscopical structure is also simplerthan in the latter, as it represents the adventitia of the supra-neural vessel modified lymphoidly and quite distinct from themembranes of the nerve-chain.

It is thus seen that the structure of the lymphatic glandsalso points to the primitiveness of the complex type of thelymphoido-phagocytic apparatus. At any rate it is an estab-lished fact that the Buthidae with their simple apparatus are

636 E. N. PAVLOVSKY

quite distinct from the Chactidae and Scorpionidae with theircomplex lymphoido-phagocytic organs which are more primi-tive phylogenetically. I must remark that C h a e r i l u s andCa lchas have not been studied by me with regard to thestructure of their phagocytic organs.

REFERENCES.

Birula, A.—" Scorpiones ", in ' Faune de la Eussie et des pays limi-trophes ; Arachnides ', vol. 1, Petrograd, 1919.

Borner.—" Arachnologische Studien, I I I " , ' Zool. Anz.', vol. xxv, 1902.Buxton, B.—" Coxal glands of the Arachnids ", ' Zool. Jahrb.', Supplem.

14, 2. Heft, 1913.Gadsikiewicz, W.—" On the histology of the circulatory system in Arach-

noidea ", ' Trans. Imp. Acad. Sci., St. Petersburg, Physico-Math. Dept.',vol. xxii, no. 7, 1908.

Cuenot, L.—" Etudes sur le sang et les glandes lymphatiques dans laserie animale. 2e partie: Invertebres ", ' Arch. Zool. exp. et gen.',vol. 9, 1891.

Kowalewsky.—" Etudes experimentales sur le cceur de quelques Ortho-pteres ", ibid., 1894.

" Une nouvelle glande lymphatique chez le scorpion d'Europe ",' Mem. Acad. Imp. Sci., St.-Petersbourg', ser. viii, classe physico-math., vol. v, 1897.

Kraepelin, K.—" Die secundaren Geschlechtscharaktere der Scorpione,Pedipalpen und Solifugen ", ' Jahrb. Hamburg. Wiss. Anat.', vol. xxv,Beitr. 2, 1908.

Laurie, M.—" Further notes on the anatomy and development of Scorpionsand their bearing on the classification of the Order ", ' Ann. Mag. Nat.Hist.', ser. 6, vol. xvii, 1896.

Livanov, N.^-" Boundary structures in the Polychaeta and the generalmorphological significance of these structures", ' Trans. Soc. Nat.,Univ. of Kazan', vol. xlvi, 1914.

Pavlovsky, E. N.—" Ein Beitrag zur Kenntnis der Giftdrusen der Arthro-poden " (mit 4 Tafeln und 10 Textfiguren), ' Trav. Soc. Nat. Petro-grad ', xliii, livr. 2, 1912.

" Scorpiotomische Mitteilungen. I. Ein Beitrag zur Morphologieder Giftdrusen der Skorpione ", ' Zeitschr. wiss. Zool.', vol. cv, 1913.

" Scorpiotomische Mitteilungen. II. Ein Beitrag zum Bau und zurEntwicklung der Giftdrusen bei den Skorpionen ", ibid., vol. cxii, 1914.

" Julek [in the district of Perovsk of the Sir-Daria Province (Turkes-tan)] and some biological observations in its neighbourhood ", ' Trav.Soc. Nat. Petrograd', xlvii, livr. 1, 1916.

STUDIES ON SCORPIONS 687

Pavlovsky, E. N.—" Sur la structure des organes phagocytaires chezScorpio maurus (L.) ", ' C. B. Soc. Biol.', vol. lxxviii, 1915.

" Sur la phagocytose chez Scorpio maurus (L.) ", ibid." Sur la structure des organes phagocytaires et sur la phagocytose

chez Scorpio maurus (L.)", 'Trans. Agric. Bact. Lab., Dept. of Agrie.,Petrograd ', vol. vi, 1916.

Pocock, R.—" How and why scorpions hiss ", ' Natural Science ', vol. ix,1896.

Houssay, F.—" Sur la lacune sanguine perinerveuse, dite artere spinalochez les scorpions, et sur l'organe glandulaire annexe ", ' C. B. Acad.Sci.', vol. civ, 1887.

Seheuring, L.—" Ueber ein neues Sinnesorgan bei Heterometrus longi-manus ", ' Zool. Anz.', vol. xl, 1912.

Sehimkewitsch, W.—" Ueber die Entwicklung von Telyphonus caudatus(L.), verglichen mit derjenigen einiger anderer Arachniden ", ' Zeitschr.wiss. Zool.', vol. lxxxi, 1906.

Schneider, A.—" Melanges arachnologiquos ", ' Tablettes Zoolog., Poi-tiers ', vol. 2, 1892.

EXPLANATION OF PLATES 81, 32, AND 83.

LETTERING.

adv, t. adventitia ; amp, glandular sac of the hair ; bar, bulb-shapedbase of the vessel; be, base of the hair; bse, base of scaphothorax ; ca,acidophils ; chr, chelicerae ; ehy, cuticle of the hypostracum ; cox, coxalgland ; ens, est, canal in the chitin; cpr, canal of the pleura ; d, diaphragm ;Ah, liver ; ea, arterial muff-valve of the heart; ecr, eotocard ; em, myocard ;cms, muscularis of the artery ; end, endocard ; / , fibrils ; Jl, fibrils of thechitin; g, cavity of the vessel; gai, alveolar gland; gen, gene, genitalorgans ; gp, gl. plicata; gv, poison gland ; gvt, gastric gland ; hp, hypo-derm ; hyp, hypostracum of the chitin ; in, cavity of the lymphoid organ ;int, t. intima of the vessel; I, lymphoid organ; ly, lymphatic gland;M, metasternum; m, muscle; n, nucleus; neph, nephrocyte; nd,nodule of lymphatic gland ; ml, nerve ; ns, nerve-cord ; nzs, nerve-cells ;o, orifice of the lymphoid-organ ; pro, pericard ; se, hair ; sn, sternoid ;st, sternum : str, stroma of the lymphatic gland ; svl, longitudinal ventralsinus ; svlo, orifice of the ventral sinus ; t, China-ink ; tc, testostracum ofthe chitin; th, thp, theca ; y, granular substance of the theca ; 7-7 V,legs ; la, sternite of the preabdomen.

PLATE 31.

Fig. 1.—Scorpio m a u r u s (L.). Part of the lower surface in theregion of the sternum. Posteriorly to the metasternum lies the ster-noid (sn-).

638 E. N. PAVLOVSKY

Fig. 2.—S corp io m a u r u s (L.). Same, but the sternoid is fused withthe metasternum.

Tigs. 3-5.—Heterometru s c y a n e u s (C. L. Koch). Replacementof the sternum posteriorly during epigenesis. Fig. 3, new-born scorpion.The sternum lies between the coxae of the II-IV pairs of legs. Cheliceraewith provisional appendages.

Fig. 4.—Idem. Pullus after the first moult. The sternum is replacedposteriorly by converging coxae of the II pairs of legs. On the cheliceraethere are no provisional appendages.

Fig. 5.—Idem. Sternum and coxae of pullus with cephalothorax4-75 mm. long. The coxae of the II pair of legs repress the sternum whichis already disposed typically.

Fig. 6.—Lychas m a r m o r e u s (C. L. Koch). Posterior replacementof the middle eyes during epigenesis. (a) The eyes are disposed near theanterior edge of the cephalothorax ; (b) the middle eyes have removedposteriorly.

Fig. 7 .—Opis thocent rus m a d a g a s c a r i e n s i s (Kr.). New-bornscorpion. Chelicerae with nagelliform provisional appendages belongingto the organs of nutrition of the embryo in the womb. The tergites andpleurae of the preabdomen bear provisional dermal spines.

Fig. 8 .—Bothriurus v i t t a t u s (Guer.) $. Transverse section ofpoison vesicle with two poison glands (gv) and glandula plicata under itssuperior concave wall. Museum specimen. Giemsa stain.

Fig. 9.—Buthus eupeus . Lymphatic gland (schematic figure).Fig. 10.—Buthus a u s t r a l i s . Ditto.Fig. 11.—Lychas m u c r o n o t u s . Ditto.Fig. 12.—Hadruroides l u n a t u s . Lymphatic gland andlymphoid

glands (schematic).Fig. 13.—Scorpio maurus . Do.Fig. 14.—Liobuthus Kess l e r i (Bir.). Pointed leg of scorpion that

had never moulted. Through its skin cells are visible.Fig. 15.—Transverse section of poison vesicle. Primitive poison glands

(type I, form A) the epithelium of which is more or less alike in height.(Schematic.)

Fig. 16.—Transverse section of poison vesicle. Complex poison glands(type II, form B2) with more than four to five true folds. (Schematic.)

. PLATE 32.

Fig. 1.—Scorpio m a u r u s (L.). Frontal section of the free marginof the tergite. Above—hard chitin with canal; below—soft chitin ofarticulatory membrane. Zenker-formol. Giemsa. Zeiss, 1/12 horn, imm.,oc. 2.

Fig. 2.—Idem. Perpendicular section of the pleura with large canalin it. Zenker-formol. Giemsa. Zeiss, 1/12 hom. imm., oc. 2.

STUDIES ON SCORPIONS 639

Fig. 3 .—Opis thophtha lmus w a h l b e r g i i (Thor.). Section ofchelicera with soaphotrix (stridulation apparatus). Museum specimen.Paraoarmine.

Fig. 4.—Idem. Stridulation apparatus (scaphotrix).Fig. 5 .—Heterometrus c y a n e u s (C. L. Koch).—Section of

trichobothrium of the chela in pullus with unpigmented integuments.Hot corrosive sublimate with acetic acid. Haematoxylin. Zeiss, obj. DD,oc. 4.

Kg. 6.—Idem. Pullus with pigmented integuments. Transverse sec-tion of chela. Alveolar dermal gland visible. High magnification.

Fig. 7.—0 d o n t u r u s d e n t a t u s (Karsch.). Hair of the ampulla of thepoison gland. Theca very narrow. Cells not drawn. Museum specimen.Giemsa's stain. Zeiss, 1/12 horn, imm., oc. 2.

Fig. 8 .—Heterometrus c y a n e u s (C. L. Koch). Embryo. Hair oftail with ampulla of cells at its base. Hot corrosive sublimate with aceticacid. Iron haematoxylin. Zeiss, obj. DD, oc. 4.

Fig. 9.—Scorpio m a u r u s (L.).—Transverse section through lym-phatic gland of a young scorpion (after Buxton's preparation). To thegland are adjacent, from above and from the left, nephrocytes (neph). Inthe tissue of the gland a differentiation into stroma fibres (str) and basalcell-elements is visible. Haematoxylin, safranin, orange. Zeiss, obj. DD,oc. 4.

Fig. 10.—B u t h u s eupeus (L.). Transverse section through the arteryperforating the liver. Hot corrosive sublimate with acetic acid. Mann-Hollande. Zeiss, obj. 1/12 horn, imm., oc. 1.

Fig. 11.—B u t h u s a u s t r a l i s (L.). Part of longitudinal section alongthe middle line of the dorsal side of the heart. Part of the supracardialnerve (nrl) with nerve-cells (nzs) along the course of the fibres are visible.Eosin-azur. Zeiss, 1/12 horn, imm., oc. 4.

PLATE 33.

Fig. 1.—Buthus (Pr ionurus) c r a s s i c a u d a (01.). Part ofhorizontal section through the embryo (late stage of development) in theregion of the III, IV" pairs of legs and the adjacent parts of the pre-abdomen. The anterior ends of the longitudinal ventral (pulmonary)sinuses (svl) are visible. After A. Birula's preparation. Borax-carmine.Zeiss, obj. AA, oc. 1.

Fig. 2.—Idem. Section from the same series of horizontal sectionsthrough the embryo, but on a higher level. The perforation of the dia-phragm by the anterior ends (svlo) of the ventral longitudinal sinuses isvisible. In the section the venous sinuses simulate the vestiges of thelymphoid organs (cp. fig. 22, PI. ii, of Kowalewsky's work, 1897). Borax-carmine. Zeiss, obj. AA, oc. 1.

640 B. N. PAVLOVSKY

Fig. 3.—B u t h u s eupeus (L.). Transverse section through lymphaticgland of the scorpion seventy-five days after injection of China-ink,hardly any of which remained in the gland. The gland of this individualis very strongly developed. Giemsa. Zeiss, ob. AA, oc. 4.

Fig. 4.—Scorpio m a u r u s (L.). Transverse section through lym-phoid organ (after Buxton's preparation). Dubosq, haematoxylin,safranin, orange. Zeiss, ob. DD, oc. 4.

Fig. 5.—Buthus eupeus (L.). Part of lymphatic gland adjacent tothe wall of the supraneural vessel, the cavity of which is connected bya slit (marked with an arrow) with the interior of the lymphatic glandinto which the muscles of the media of the supraneural vessel also pene-trate. Giemsa. Zeiss, obj. 1/12 horn, imm., oc. 2.

Fig. 6.—Buthus a u s t r a l i s (L.). Part of transverse section of thelymphatic gland after repeated injection of 1 per cent, aqueous solutionof coUargol which has impregnated the connective-tissue stroma of theorgan. In the cavity of the gland and exteriorly, between its nodes, thereare numerous acidophils (ca). Formalin. Giemsa. Zeiss, obj. DD, oc. 4.

Fig. 7 .—Anomalobuthus r i c k m e r s i (Krpln.). Glandular-sensi-tive hair of comb-shaped appendage. Carnoy. Mann-Hollande stain.Zeiss, 1/12 horn, imm., oc. 4.

Fig. 8.—Transverse section of poison vesicle. Primitive poison glands(type I, form A) with few false folds (with an epithelium of varyingheight).

Quoit kiniMff.Sri.VolMNlPl.3l

JS/IC

E.Partot'tky deL