9© Journal of Comparative Neurology. 



Sylvian fissure in my Hippopotamus is quite evident and within 

 it I noticed a rudimentary island of Reil." 



THE INSULA IN THE CETACEA. 



Fig. 35 represents the insula of the porpoise [GlobioccpJi- 

 ahis mclas). In this specimen the insula is completely con- 

 cealed within the Sylvian fissure and the plane is parallel to 

 the lateral surface. The area is proportionally very large but 

 at the same time very flat and there is no evidence of a fis- 

 sure homologous with the transinsular and no approximation to 

 a pole. This specimen shows at least nine gyres, three of 

 which are subdivided by fissures which are deepest near the 

 circuminsular. It is not known that any of the fissures of this 

 area are constant. In 1879 Spitzka (53) says the " insula in the 

 porpoise has four times as many convolutions and is twice as 

 large as that in man and is completely covered by the opercu- 

 lum and temporal lobe." The same author also says that one 

 specimen in his posssession has either thirteen or fifteen gyres. 

 Wilder [lecture] said that the gyres of the porpoise insula ex- 

 ceed in number those of any other mammal observed by him, 

 but they are smaller, and he concluded that ' ' in combined 

 elevation and fissuration, the insula reaches its highest devel- 

 opment in man." 



Ziehen (31^ 1 10, 1889) says of the white whale {Bebiga 

 lucas), " The area between the fissura circularis interna and the 

 fissura circularis externa, probably also a large part of the cov- 

 ered portion of the floor of the Sylvian fossa ought to be desig- 

 nated as insula." Of the Sylvian fissure in Mcgaptcra hoops, he 

 (31, 125) says " Ursprung vom aus der Fissura Rhinalis An- 

 terior. Die Haupttheil bildet die obere Begrenzung des 

 Inseldreiecks." 



None of the representatives examined of the remaining 

 orders show any evidence of an insula. 



