THE CEKEBEUM OK PEOSENOEPHALON. 



163 



frontal lobe, for the Pokis occipitalis, temporal lobe, etc. But this is in- 

 correct, since that which bears the name in mammals is a product of late 

 development. For example, the occipital lobe of mammals does not exist at 

 all in reptiles. It appears for the first time in birds. The occipital lobe is 



Fig. 110. — Schematic sagittal section of a reptilian brain. 



not alone a prominence of the occipital pole, but a definite portion of cere- 

 brum with a specialized cortical character and a fixed relation to the origin 

 of the Opticus. 



So we find that even in the lower yertebfates the form of the brain 



Fig. 111. — Schematic sagittal section of an avian brain. 



varies in different orders. When, for example, one compares the above 

 illustrated lizard-brain with that of a turtle the compressed form of the 

 latter will certainly be apparent. It is brought about, on the one hand, by 

 the development of the striatum, which, as above described, causes a simi- 



