376 



ZOOLOGY 



SECT. 



The medulla oUongata (m. o.) has a well-marked ventral flexure, as 

 in the Lizard. The cerebellum (cb.) is of great size, and has a large 

 median portion and two small lateral lobes orflocculi (/.) ; the surface 

 of the middle lobe is marked by grooves passing inwards in a 

 radiating manner and carrying with them the grey matter, the 

 extent of which is thus greatly increased. The metaccele (Fig. 987,^4) 

 is completely hidden by the cerebellum, and the latter is solid, 



pn 



\ 



O.I 



olf 



FIG. 986. Columba livia. The Brain ; A, from above ; B, from below ; C, from the left 

 side. cb. cerebellum ; c. 7t. cerebral hemispheres ; /. flocculus ; inf. infundibulum ; //;. o. 

 medulla bblongata ; o. 1. optic lobes ; o. t. optic tracts ; pn. pineal body ; II XIII, cerebral 

 nerves ; sp. 1, first spinal nerve. (From Parker's Zootomy.) 



having no epicoele. The hemispheres (c. Ji.) extend backwards 

 to meet the cerebellum, and the optic lobes (o. I.) are thereby 

 pressed outwards so as to take up a lateral instead of the 

 usual dorsal position : they are of rounded form, and each 

 contains an optoccde (Fig. 987, A, o. v.) opening from a narrow 

 passage, the iter, which represents the original cavity of the 

 mid-brain. A further result of the extension of the hemi- 

 spheres and cerebellum respectively backwards and forwards is 



