942 



EVOLUTIONAL MODIFICATIONS 



exceed a forebrain index of 60 per cent. In the main they are all much Ix'Iow 

 this figure. The forebrain indices in the dogfish, codlish and shark are ail 

 less than 25 ]>er cent of the total brain \-ohime. A reptihaii form, such as 

 the soft-shelled turtle, shows the considerable advance to 53 per cent, 

 while the American ostrich w ith 60 per cent reaches the high level of develop- 

 Encephalic Indices of Evolitional Significance 



I Icmo sapiens, modern man 



Troglodytes gorilla, gorilla 



Simia satyrus, orang-outang. . 

 Macacus rhesus, Indian monkey 



I lylobates hoolock, gibbon 



Callithrix jacchus, marmoset.. . 



Index: 70 to 80 



iilliaris, dog 



icstica, cat 



ballus, hors 



js, cattle 



bachtr., camel. . 

 ndicus, elephant 

 )phaga jub., g 



5 tridact., three-t 

 Index: 20 to 60 



88 



83 



82 



83 



14 

 15 



16 



I liii)fs Claws 



Wings Fins Paddle? 



