CORTICAL LOCALISATION 299 
second factor in growth antagonism—restricted intracranial 
space—as the chief cause. The skulls of all these animals 
named are adapted to special purposes—that of the carnivora 
for the seizing and killing of prey, necessitating very powerful 
temporal muscles with great buttresses of bone to give wide origin 
to them. In the ungulates the head is modified for the cutting 
of food from the surface of the ground and for providing a large 
area for the grinding of herbs. 
In the eetacea the head end of the body has to be kept small 
to enable the animal to plough the water with the least. possible 
resistance, whilst at the same time these animals possess an 
enormous body weight which has to be represented in their 
brains. So that it is not surprising that the amount of con- 
volutioning in the cetacea should be, as it is, greater than in the 
carnivora and most of the primates. In the primates the 
existence of the prehensile paw allows the skeleton of the face 
to be reduced to a minimum so that more space can be allowed 
the brain, and the weight of the skull still be within supportable 
limits. 
CONCLUSIONS 
1. That to say that furrow formation depends alone either on 
cortical specialisation or on growth antagonism is not to be 
sufficiently explicit. 
2. That furrow formation depends primarily on evolutionary 
antagonism between the neopallium which is constantly ac- 
quiring new areas, and its fibro-osseous capsule, the skull. 
3. That the furrows thus originated tend to appear at the 
edges of areas possessing cyto-architectural differences. 
4. That in the primate brain furrow formation depends on 
constant factors throughout the order. 
5. That the highly convoluted brains of carnivora, ungulata 
and cetacea argues a mode of origin different from that existing 
in the primates. 
