No. 390.] REVIEWS OF RECENT LITERATURE. 519 
GENERAL BIOLOGY. 
Effect of Chemical and Physical Agents upon Growth. — The 
second part of Dr. Davenport’s useful Experimental Morphology * will 
be welcomed by all students of the theoretical aspects of biology. 
This volume deals with the effects of external conditions upon 
growth. The first chapter is devoted to the consideration of the 
phenomena of normal growth, which is defined as increase in vol- 
ume. Three factors are recognized — increase of formed substance, 
of plasma (protoplasm), and of enchylemma. Special emphasis is 
laid on the importance of the imbibition of water at the period of 
most rapid growth. Characteristic curves are given showing at first 
a rapid increase in the rate of growth, which soon reaches a maxi- 
mum, and then more gradually declines to zero. The final cessation 
of growth is to be explained by special reasons for each species, and 
is not due to any general law. 
The following chapters treat of the effects upon growth of chemi- 
cal agents, water, density of the medium, molar agents, gravity, elec- 
tricity, light, and heat. In each of these the effect of the agent 
considered is treated first in regard to its effect upon the rate of 
growth, and then as to its effect upon the direction of growth. The 
molar agents affecting growth include contact, rough movements, 
deformation, wounding, and the flow of water. A final chapter is 
devoted to the effects of certain complex agents upon growth and to 
general conclusions. 
The book has comparatively little to do with theory. It is essen- 
tially a very careful and complete résumé of the records of laboratory 
experiments in the field which it covers. The only experiments that 
have not been published before are those described on page 365. 
They were made by Messrs. Frazeur and Sargent in the zodlogical 
laboratory at Harvard, and their object was to determine the effect 
of concentration of medium upon the rate of regeneration and fission 
in certain annelids — a species of Nais and Dero vaga. This lack of 
newness does not lessen the value of the work, however. A glance 
at the extensive bibliography at the close of each chapter is enough 
to convince one of the service that the author has performed for 
biology by bringing together this immense amount of material in so 
compact and accessible a form. 
1 Davenport, C. B. Experimental Morphology, Pt. ii. Effect of Chemical and 
Physical Agents upon Growth. New York, Macmillan, 1899. pp. 281-509. Illus- 
trated, 8vo. 
