COORDINATION AND BEHAVIOR 



545 



cerebellum depends on the swimming ability 

 of the species. In amphibians the olfactory 

 lobes are large and elongated; the optic 

 lobes are smaller; the cerebellum is a mere 

 transverse band; and the medulla is pro- 

 duced by a broadening of the spinal cord. In 

 reptiles the olfactory lobes are usually not 

 well developed; the cerebral hemispheres are 

 much larger and a little gray matter is pres- 

 ent in the cortex; the optic lobes are quite 

 small and the cerebellum is larger; and both 



pineal and parietal bodies are present, the 

 latter forming a median eye in Sphenodon. 

 In birds the brain is short and broad; the 

 olfactory lobes are very small; the cerebral 

 hemispheres are large, but the gray matter 

 is limited to the posterior region; the optic 

 lobes are comparatively large and spread 

 apart by the large cerebellum. In mammals 

 the olfactory lobes are well developed; the 

 cerebral hemispheres are very large, due to 

 the growth of the gray matter in the cortex; 



Olfactory lobe 



Cerebrum 



.:j Pineal body 

 Optic lobe 



Cerebellum 

 Medulla 

 Spinal cord 



CYCLOSTOME (Lamprey) 



FISH (Perch) AMPHIBIAN (Frog) 



Olfactory lobe 1 | Olfactory lobe- 



^'^Cerebrum 



Pineal 

 body 



^Optic lobe 

 Cerebellum 



Medulla 



Spinal cor 



Cerebrum 



Cerebellum 



Medulla 



Spinal cord 



REPTILE (Alligator) 



BIRD (Pigeon) 



OJI 



MAMMAL (Cat) 



Figure 392. Diagrams showing the dorsal surface of the brain of 6 types of vertebrates and 

 designed to illustrate differences in the degree of development of the different parts. Note espe- 

 cially the progressive increase in size of the cerebellum and cerebrum. 



