XIV. 9 (3 8 3) 



9. Nervous system and receptors of reptiles 



All the modifications of structure that fit the reptiles for life on 

 land would be useless without the development of appropriate be- 

 haviour. This in turn depends on suitable structure and function of 



cer.h. 



cLf.b. 



<?** warn 



hypoth. 



Fig. 216. Three views of the brain of a lizard. 



cereb. cerebellum; cer.h. cerebral hemispheres; hypoph. hypophysis; 



hypoth. hypothalamus; olf.b. olfactory bulb; tect.opt. tectum opticum; 



II— XII, cranial nerves. (After Frederikse.) 



the nervous system. The brain accordingly shows some interesting 

 developments. The cerebral hemispheres are relatively larger in 

 reptiles than in amphibians (Fig. 216). The increased bulk lies mainly 

 in the basal parts of the hemisphere (the corpus striatum), as in birds 

 (Fig. 217). The roof (pallium) is little developed and lacks the elabor- 

 ate cortical differentiation found in mammals. The thalamus is well 

 developed and receives connexions from the optic tracts, which no 

 longer run mainly to the midbrain. There are also many fibres from the 

 thalamus to the cerebral hemispheres. This, together with the other 

 features mentioned, may be evidence for the transfer of many nervous 



