PHYSIOLOGY: S. HATAI 
19 
at pleasure so long as the collimator is fixed. This is often a great conveni- 
ence in working with the achromatic fringes; but I will pass these details 
over here. 2 
1 These Proceedings, 3, 1917, (563). In this note the glass paths, which are of less 
importance than the air paths, are too much accentuated. 
2 Abridged from a Report to the Carnegie Institution of Washington, D. C. 
THE BRAIN WEIGHT IN RELATION TO THE BODY LENGTH AND 
ALSO THE PARTITION OF NON-PROTEIN NITROGEN, IN THE 
BRAIN OF THE GRAY SNAPPER (NEOMAENIS GRISEUS) 
By Shinkishi Hatai 
Tortugas Laboratory, Carnegie Institution of Washington, and The Wistar 
Institute of Anatomy and Biology 
Communicated by A. G. Mayer, December 24, 1917 
The predatory fish called the gray snapper, N. griseus was mainly used for 
the present investigation, which was conducted at Tortugas, Florida in the 
summer of 1917. The following are the more important facts brought out. 
1. The Brain Weight in Relation to Body Length. — Altogether observations 
have been made upon 74 brains of the gray snapper. It was found that the 
relation of brain weight to the increasing body length, from 150 mm. upward, 
is practically linear and may be satisfactorily expressed as y = a + bx, where 
y represents brain weight in grams and x the body length in millimeters, and 
a and b are the constants with the values, in this instance, —0.333 and 0.00433 
respectively. (Body length is measured from the tip of the snout to the crotch 
of the tail. ) 
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 1 but it is remarkable to find the linear relation in fish, when they 
are so small. This linear relation during the period of early growth probably 
means that in the snapper the brain reaches its structural maturity early, 
and that the subsequent increase in weight indicates merely a uniform swell- 
ing of the nervous tissue as a whole. 
On account of scantiness of the data for specimens less than 200 mm. in 
body length, I am unable to present a complete 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 is linear. 
Kellicott 2 studied the growth of the brain in the smooth dogfish in respect 
to the body weight, and found the graph to resemble that of the mammalian 
brain (logarithmic curve) and thus to differ strikingly from that for the gray 
