1897. Zoology. 619 
nearly every accredited high school is now using the compound micro- 
scope in the study of plants selected as types of all the greater groups 
of the vegetable kingdom. We may be permitted to remark, also, 
that in practice it will be found impossible to secure in nine-tenths of 
the secondary schools, much of the material suggested by the author 
for study. In many chapters the teacher may readily make substitutions, 
but ın those relating to epiphytes, parasites, saprophytes and insecti- 
vorous plants, this difficulty will prove quite embarrassing. 
—CHARLEs E. Bessey. 
ZOOLOGY. 
The orientation of organisms by light.’—The problem that the 
author undertakes to solve is whether the migration of organisms to- 
wards or from a source of light is due to differences in intensity or to 
the direction of the rays. According to Strasburger, whose views have 
been more or less generally accepted, the determinant factor is the 
direction of the rays. His conclusions drawn from experiments with 
swarm spores of Botrydium and Bayopsis (78) were later (90) confirmed 
by Loeb in experiments with the larve of Porthesia chrysorrhea. But 
this view of the subject has been opposed by Oltmann (92) as the 
result of certain experiments performed with Volvox minor and glob- 
ator; and Oltman has been supported by Verworn (94). ` 
Davenport and Cannon criticise Oltman’s management of his appara- 
tus and themselves attack the problem with what is essentially the 
method of Strasburger, but use Daphnia instead of plants. A small 
glass trough was painted dead black inside and out and placed on a 
table at a distance, at its nearest end, of 51 cm. and of 66.5 cm. at its 
further end, from the light of a gas lamp having a Welsbach burner 
Which was raised 31 cm. above the table. A wedge shaped box with 
glass bottom and filled with India ink solution served, when needed, as 
a screen, the thicker portion of the wedge being placed nearest the 
Source of the rays. 
Experiments without the screen showed that the Daphnis when 
introduced at the end of the trough farthest from the source of light 
1C. B. Davenport and W. B. Cannon. On the Determination of the Direction 
and Rate of movement of organisms by Light. Reprint from Journ. Phys. XXI, 
22-32. From Dr. C. B. Davenport. 
