14 Journal of Comparative Neurology and Psychology. 



Showing Varutions in the NIedullaey Sheath. 



Shark' 

 Spec. 



FroO 



Spec, 



XI 



To-lle 

 Spec. 



xxn 



Chick 

 Spec. 



he: 



Spec. 



Yxmn 



Man 

 Spec. 



Averaoe 

 percenla6e 

 Ideal. deWalion. 



Avera<)e Exlreme voriolious. 

 observed. + 



o - o o o 

 o o o o 



o • o o o 



O ' o o o 



+0.9 O O 



O " o o o 



Figure 1 



