CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF 
THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 
COLLEGE. E. L. MARK, DIRECTOR. No. 117. 
STUDIES ON THE CAUSE OF THE ACCELERAT- 
ING EFFECT OF HEAT UPON GROWTH. 
ti W. GALLOWAY: 
Tue following studies, directed toward a further analysis of 
the fact that the rate of growth of organisms varies with tem- 
perature, were made at the suggestion and with the guidance 
of Dr. C. B. Davenport. Growth, defined as increase in 
volume or mass, is evidently produced by one or both of the 
following processes: either (1) by imbibition of water, which 
results in an increase of cell sap, or (2) by assimilation, ze., 
anabolic metabolism, which results in the increase of plasma 
and of formed substance, such as starch, cellulose, etc. The 
question to which an answer was sought is this: In the 
acceleration of growth due to higher temperature, are imbibi- 
tion of water and anabolic metabolism equally accelerated ? 
or, if unequally affected, in which process is acceleration most 
marked ? 
The procedure embraced the following points : 
1. Experiments were made upon the larvae of Rana sylves- 
tris, Amblystoma punctatum, and Bufo americana. 
2. Fertilized eggs of a single spawning were subjected to 
three different temperature conditions: (1) 6?-8? C., (2) 12?— 
18? C. (12?—- 15? C. in Rana), and (3) 22?-25? C. (20?-24? C. 
in Amblystoma) The other conditions were as nearly as 
possible alike in the three cases. 
3. No food was supplied other than that contained in the 
egg and in the albumen surrounding the embryo; consequently, 
these results apply only to the early stages of development in 
the amphibian embryo. 
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