A. Dogfish 



ArchipaUium- 



"^Ventral nuclei 



Cerebral nuclei 



Cortex 



C. Alligator 



B. Frog 



Neopallium 

 Cerebral nuclei 



Ventral nuclei 



Cortex 



D. Monotreme 



Convoluted cortex 



E. Primitive Placental 



Fig. 164. Cross Sections through the Cerebral Hemispheres. Observe the 



development of cerebral nuclei in the Frog (B), and a cerebral cortex in the 



Alligator (C). The cortex increases in size in the Monotreme, and becomes 



convoluted in higher mammals. 



