A NOTE ON THK CKREBRAL FISSURATION OF 

 THE SEAL (Phoca vitulina).' 



PiKKKE A. Fish, D.Sc. , 



Bureau of -Iniiiial /nJushy, Washington, D. C. 



The specimen was not more than one year of age, and came 

 into my possession in November, 1895. During the manipu- 

 lation incident to the process of hardening some general resem- 

 blance of the fissural pattern to that of the feline or canine type 

 was noticed. The pia was removed and the fissures studied at 

 an intermediate stage of the hardening before their walls had 

 lost their pliancy. 



Dr. E. C. Spitzka (1890) in a preliminary paper (Ameri- 

 can Naturalist, XXVI, i 15-122) refutes some rather grave mis- 

 representions by Theodor, 1887 (Das Gehirn des Seehundes, 

 Inaugural Dissertation) one of them being the existence of 

 a so-called Co^nmissura Suprema an elongated transverse mass 

 of fibers lying dorsal to the Callosum, an artifact pure and sim- 

 ple. Theodor further states that "the Seals and (ordinary) 

 Carnivora are in their cerebral organization today widely sep- 

 arated and their common origin must be sought in a remote 

 geological period." In regard to this Spitzka states that the 

 examination of a series of brains beginning with the mink, the 

 fresh and salt water otters and passing through the eared to the 

 earless seals would show^ about as beautiful a transition as a 

 morphologist could well desire. 



In the specimen at hand the frontal region of the brain is 

 very much fore-shortened and gives the appearance of consider- 

 able width. On the lateral aspect the Sylvian fissure is well 

 marked and pursues its usual dorso-caudal course. Just in front 

 of it and extending vertically (dorso-ventrally) is another un- 



' Read at the Meeting of the American Anatomists Dec, 1895, Philadel- 

 phia, Pa. 



