10SINEAVRIEET.O.8,N.23

B & L DISSECTING MICROSCOPES

DESIGNED TO SATISFY CLASSROOM REQUIREMENTS

B & L Dissecting Microscopes offer the convenience and ruggedness neces-

sary to routine dissection in the school laboratory.

The B & L Dissecting Microscope W (illustrated) has a substantial horse-

shoe base, a removable glass stage, detachable hand rests and a rack and

pinion adjustment for focusing. A 50 mm plane and concave mirror is

mounted beneath the stage.

Magnifications from 7X to 20X are possible with Doublet, Coddington or

Triple Aplanat lens. Magnifiers are carried on an arm with two joints per-

mitting coverage of any portion of the 60 x 80 mm Stage.

Write for complete details of this and other B & L Dissecting Microscopes.

Bausch & Lomb Optical Co., 642 St. Paul St., Rochester, N. Y.

AMACA~~sARMs <

SCIENCE-ADVERTISEMENTS VOL. 86, NO. 223210

OCTOBER 8, 1937 SCIENCE-ADVERTISEMENTS

Just Published! by

E. GRACE WHITE,

V,1D1vT10"~~~~~~~~~~~~~~Ph.D.,

ICLI' jretn Professor of Biology,

tion1ge

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boa n 0jeXanI %*st geV $ e~a b-at ee9,a

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problems ofilif ohe interations intrreainsoqivnUrgnshes I i-eg oe

A LABORATORY MANUALof GENERAL BIOLOGYArranged to follow the author's "GENERAL BIOL-OGY." The exercises in Part I of the manual cover

the sections on "THE UNITY OF LIFE " and"PROBLEMS OF BIOLOGY" of the large text, andare performed in one semester with four hours of lab-oratory work each week. The exercises in Part II andPart III cover the series of plant and animal typesbased on the plant of progressive organization presented

by E. GRACE WHITE236 Pages. Price, $1.50

in the section on "THE PLANT AND ANIMALKINGDOMS" of the large text. The work in eachseries has been made sufficiently complete to allow a

full semester 's work on that series. Instructors who

teach only animal biology, or plant biology, therefore,can use the manual by omitting one section. Otherinstructors can select exercises from the two sections.

THE C. V. MOSBY CO.-3525 Pine Blvd.-ST. LOUIS, MO.

11

12 .WIENCE-ADVERTISEMENTS

PULFRICH PHOTOMETER(Arranged as Colorimeter)

This instrument is designed for colorimetry with-out comparison solution. It measures the absorp-tion occurring in different wave-length regions witha degree of precision formerly obtainable only witha spectro-photometer. The results are rapidly de-termined by one measurement without variation ofthe depth of liquid.

Additional accessories equip this instrument as aNephelometer, Glossimeter, and Comparison Micro-scope. Literature will- be gladly sent on request.

CARL ZEISS, INC.4 8 5 F i ft h Ave nu e 728 So. Hill StreetN E W Y 0 R K L LOS ANGELES

3E.N

12 SCIENCE-ADVERTISEMENTS VOL. 86, NO. 2232