Optic Lohes of Foivl. 87 



ceding stage ; they have sunk slightly towards the ventral sur- 

 face. The cerebellum has become enlarged, and is now the most 

 prominent feature of the brain dorsally. Nine convolutions 

 are visible from this view, and the flocculi are becoming dis- 

 tinctly marked. The medulla^ remains much as at stage YI. 



7c (Fig. 7, Section 1) is taken from the most anterior portion 

 of the optic lobes. On the dorsal surface the epiphysis is cut 

 through, and on the ventral the optic chiasma is seen. The 

 walls of the lobes only are seen, for the section is anterior to 

 the op'tocoele. 



7d (Fig. 7, Section 2) shows a section at about the centre of 

 the lobes. The brain substance is rapidly increasing in such a 

 manner as to tend to fill the cavity of the optic lobes, so that 

 the optocoele is now becoming luuch diminished in size. The 

 crura cerebri are w^ell developed. 



In 7e (Fig. 7, Section 3) the posterior portion of the optic 

 lobes, with the posterior portion of the optocoele, is seen. The 

 cerebellum has assumed a very characteristic and definite shape 

 and position by this time. 



Stage VIII. PI. XXXIT.) 



The eighth stage corresponds approximately to a period of 

 16 days' incubation. 



In the dorsal view the cerebral hemispheres are seen to have 

 become more triangular in shape than in the preceding stage. 

 The cerebellum is growing forward so as to reach the posterior 

 region of the cerebral hemisplieres, and is overshadowing the 

 epiphysis posteriorly, while the quickly enlarging cerebral 

 hemispheres are beginning to hide it somewhat anteriorly. 

 Eight distinct convolutions can be seen in the cerebellum at this- 

 stage, and the flocculi are becoming steadily more definite. 

 The optic lobes are now most distinctly becoming overgrown and 

 pushed down by the cerebral hemispheres and cerebellum, and 

 are moving out and down to their tiiial ventro-lateral position. 

 The medulla is much as in the preceding stage. 



The lateral view (8a) shows how very prominent the cere- 

 bellum has by this time become. Nine distinct convolutions 

 are visible, and the fiocculi are more distinct. The cerebral 



