z68 



COMPARATIVE MORPHOLOGY OF VERTEBRATES 



pbiones, they are paired, but the mid-brain is without external division in the 

 urodeles. The cerebellum is very small, a mere transverse fold on the anterior 

 border of the fossa rhomboidalis, which is scarcely covered in front. 



Fig. 176. — Dorsal and ventral views and sagittal section of brain of Desmognathust 

 after Fish, a, anterior commissure and rudimentary corpus callosum; c, cerebrum; clt 

 cerebellum; cp, chorioid plexuses; e, epiphysis; h, hypophysis; i, infundibulum; oc, optic 

 chiasma; ol, optic lobes; p, paraphysis; pc, posterior commissure; sc, superior commissure; 

 I-X, nerves. 



REPTILES. — In the reptiles the brain shows a considerable range of struc- 

 ture, all showing an advance over the amphibia, especially in the greater relative 

 size of the cerebrum, which exceeds the mid-brain, and in the development of 

 a cortex in the pallium. Something is retained of the pontal and nuchal flexures 

 (fig. 178, side view). The cerebral hemispheres are oval or triangular and often 



