THE 
AMERICAN NATURALIST 

VoL. XXIV. FEBRUARY, 1890. 278. 

REMARKS ON THE BRAIN OF THE SEALS. 
BY E, C. SPITZKA. 
FE NGAGED for many years in collecting material for a mono- 
graph on the “ Marine Mammalia,” whose publication has 
been delayed by the obtaining of new specimens from unexpected 
sources, and partly by the desire to publish only well-matured 
and verified observations, I find myself compelled to anticipate 
my projected paper, in order to correct the manifest errors of the 
latest publications on this subject. 
Dr. Fritz Theodor! makes the startling discovery that in the 
Phoca (Calocephalus) vitulina there is between the two cerebral 
hemispheres, dorsad of and separated by a gyral interval from the 
callosum, a second commissure, extending cephalo-caudad nearly 
as much as that great fiber-bridge. Such an observation would 
revolutionize all ideas hitherto accepted as to the signification and 
relations of the callosum, not to mention the peculiar position 
which such a profound deviation from the mammalian cerebral 
type would lead morphologists to assign the Phocide. 
On examing Theodor’s plate (x., Fig. 4) I find that his so-called 
“ commissura suprema” is the saddest kind of a delusion. In 
making a medi-section of his seal’s brain he sliced off a mesal 
gyrus, and, deceived by the cut surface, hastily assumed it to be 
a commissure. How carelessly this was done becomes evident 
1 Das Gehirn des Seehundes (Phoca vitulina: Dr. Fritz Theodor, Freiburg i. B., 1887. 
(The Brain of the Common Seal, by Dr. Frederick Theodor.) 
