862 



COMPARATIVE ANATOMY 



capsules and consist of three semi-circular canals, a utriculus, and a 

 small simple sacculus. The lateral line sense organs are in grooves of 

 the skin not completely closed. They divide into several branches in 

 the head region, one above and one below the eye, and some in the hyo- 

 mandibular region. 



TELEOSTS 



The vertebral column is not very compact, the vertebrae being often 

 without a centrum. If the latter is present, it is an arch-centrum. The 

 nasal tract has no naso-oral groove. It opens by separate nares. The 

 brain Has a much reduced cerebrum with all olfactory lobes. The pallium 

 is usually non-nervous, causing the cerebrum to consist largely of the 

 corpus striatum. The cerebellum is larger than a surface view shows be- 

 cause a great portion projects into the ventricle. 



AMPHIBIA 



The cerebrum is larger than the optic lobes, while the olfactory bull) 

 is separated from the cerebrum by a long tract. The various brain parts 

 are quite distinct. In the tailless amphibia the two halves of the cere- 

 brum are secondarily connected by a transverse band behind the olfac- 



tory lobes so that a gap is left farther 

 back. 



The telencephalon is larger than 

 in fishes on account of the pallium 

 being invaded with nervous matter 

 on the inner side. There is no true 

 cortex. 



The optic lobes are large and 

 the pineal gland reaches the cranial 

 roof in the tailless amphibia. In the 

 gymnophiones there is a pontal 

 flexure which brings the pituitary 

 gland beneath the medulla ob- 

 longata. 



REPTILIA 

 \ '-- -"ii\7 



There is an advance in the nerv- 



ous system beyond the amphibia. 

 The cerebral hemispheres are larger 

 and the cerebellum more complete 

 and a cortex is developed. Some- 

 thing of both pontal and nuchal flex- 

 ures is retained. There may be a be- 

 ginning of a temporal lobe. A parietal 

 It is rudimentary in other groups. 

 The olfactory lobes are merged in the hemispheres. The eyes are small, 

 the pupil round, and the iris unusually dark in color. The thalamt de- 



n 



: ' 



' 



Fig. 483. 



Side and dorsal views of young Alligator. 

 <?, cerebrum ; cl, cerebellum ; e, epiphysial 

 structures ; h, hypophysis ; i, inf undibulum ; ol, 

 optic lobe^ ; 1I-XII, cranial nerves. (From 

 Kingsley after Herrick.) 



eye is well developed in lacertilia. 



