46 SHINKISHI HATAI 
to the increasing body length from 150 mm. upward is_ practi- 
cally linear. This linear relation between these two characters 
is better shown by the positions of the averaged values, which 
are also plotted. It is well known that in the adult stage the 
relation between brain weight and body length or body weight 
is practically linear, even in the case of some mammals (see for 
instance growth of brain in weight in the albino rat in respect 
to body length or body weight, Donaldson, ’09) but it is re- 
markable to find the linear relation in fish when they are so 
small. This linearity during the period of early growth prob- 
ably means that in the gray snapper the brain reaches its struc- 
20 
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A SHEDS See PR OSB SeomeGe se Sas le 0 
0) 50 * 100 150 200 250 300 350 400 450 
Chart 1 Showing the weight of the brain of the gray snapper according to 
body length. The observed weights are represented by 74 fish. e = observed 
weight — 0 — 0— = average observed weight (table 2). 
tural maturity early, and that the subsequent increase in weight 
indicates merely a uniform swelling of the nervous system as 
a whole. The maturity of the brain at a relatively early stage 
of growth may be inferred also from practical constancy of the 
percentage of water in the brain from the very small to the very 
large fish in this series (page 48). 
It is to be regretted that it was not possible to obtain data on 
smaller specimens, though every effort was made to obtain such 
specimens while I was at the Tortugas Laboratory. We were 
even unable to find any of the gray snapper fry, though the fry 
of the school master (Neomaenis apodus) which is most closely 
