OPTIC THALAMI CEREBRAL LOBES. 2O 



In front of the optic lobes, in batrachians and those reptiles in which 

 the cerebral lobes extend but little posteriorly, transverse sections show 

 simply two symmetrical masses, joined below and diverging above, one 

 on each side of the V shaped third ventricle. These are the optic thai- 

 ami. Underneath are the tuber cinereum with its ventricle, and the hy- 

 pophysis cerebri. 



THE CEREBRAL LOBES. 



PLATE XCII. shows a section made through the anterior portion of the 

 third ventricle so as to include the lateral ventricles of the cerebrum, with 

 the choroid plexus in the median fissure. This fissure, in another plane, 

 communicates with the lateral ventricles, forming the ventriculus com- 

 munis of Stieda. 



Plate XCI. is from a section made through the middle of both cere- 

 bral lobes, and represents the protuberances on their inner walls, the 

 lower pair being the corpora striata. The caudate cells of one of the 

 upper protuberances are demonstrated in Plates XCIII. & XCIV.* 



Plates LXXXVI. XCVIII. furnish evidence of the similarity in 

 the general arrangement of parts in the cerebral lobes of these animals. 

 In those from saurians and ophidians, the development of the corpus stri- 

 atum is seen to exceed greatly that of the same organ in batrachians. 



Plate LXXXVI. from heloderma, shows much the same configura- 

 tion that is found in the alligator, although the corpus striatum is rel- 



* These protuberances are erroneously named : corpora striata, under Plates XCII. 

 XCIII. & XCIV. 



