METABOLIC ACTIVITY OF NERVOUS SYSTEM 47 
related to the gray snapper, was abundant everywhere. Pos- 
sibly the months of June and July were not a proper season to 
find them, or the fry of the gray snapper may not live in the 
open seas or along the beach, but may be in hiding under the 
intricate roots of mangroves, a tree not found on the Tortugas 
Islands. 
On account of the scantiness of the data on the gray snapper 
less than 200 mm. in body length, I am unable to present a com- 
plete record of the growth of the brain. However it appears 
from the general trend of the growth curve that, with the possible 
exception of the very early period, the relation between the 
brain weight and body length does not deviate much from 
linearity. 
Kellicott (08) who studied the growth of the brain in the 
smooth dogfish (Mustelus canis, Mitchill) in respect to the body 
weight, found the graph to resemble that for the mammalian 
brain; that is the graph shows a rapid rise at the early period 
which is followed by a slower rate of growth. The form of the 
curve suggests a logarithmic formula such as was used to repre- 
sent the growth of the brain in the albino rat (Hatai, 09). In 
other words the form of the graph for the gray snapper is strik- 
ingly different from that for the dogfish. This difference may be 
due to the fact that in the dogfish the brain possesses a voluminous 
cerebellum, as well as olfactory bulbs, and the combined weights 
of these two structures may be greater than that of the rest of 
the brain, while these two structures in the gray snapper are 
very small and the latter was not included. It appears that 
these two parts, olfactory bulbs and cerebellum, of the dogfish 
brain grow very rapidly during the earlier period, thus giving 
the form of the graph similar to that for the mammal. 
Since the brain weight of the gray snapper shows a linear 
relation to the body length through a wide range, and since the 
fish which are usually caught fall within this range, I have de- 
vised the following formula for brain weight on body length, 
in hopes that it may prove useful for some future investigation. 
Brain weight (gms.) = 0.00433 Body length (mm.) — 0.333. 
The results of the calculation are given in table 2 and there 
