88 K. K. Oliver: 



hemispheres are now above the optic lobes on the dorsal surface, 

 and the optic lobes are moving down in a more or less directly 

 dorso-ventral line. The ventro-lateral depressions of the cere- 

 bral hemispheres are becoming somewhat less distinct. The 

 medulla is much the same as in stage VIII. 



8c (Fig. 8, Section 3) is taken across the most anterior part of 

 the optic lobes, the cavity of which is seen to be fast becoming 

 filled by the growth of the brain substance composing its Avails. 

 The anterior lobe of the cerebellum can be seen in the median 

 line, having by this time grown forwards and upwards until it 

 is most prominent dorsally. 



8d (Fig. 8, Section 2) shows a section across the middle of the 

 optic lobes. The cerebellum can be seen to have assumed a pro- 

 minent dorsal position in the sagittal plane. The optic lobes 

 are sinking lower. 



8e (Fig. 8, Section 1) is a section across the posterior part of 

 the optic lobes, at the spot where the optocoele is almost 

 obliterated. The cerebellum is beginning to assume its rela- 

 tively large adult size. 



Stage IX. (PI. XXXIII.) 



The ninth stage corresponds approximately to a period of 

 eighteen days' incubation. 



Dorsally there is very little change from the preceding stage 

 to be seen. The cerebral hemispheres have increased slightly in 

 size, and overhang the optic lobes on the dorsal surface rather 

 more than in the previous stage. The cerebellum is enlarging 

 still, and now shows nine convolutions from this vieAv ; the 

 flooculi have become definitely established, and are now a 

 characteristic feature of the brain. The epiphysis is compara- 

 tively insignificant in size, though a distinct structure. The 

 most anterior portion of the cerebellum has grown forward in 

 such a way as to meet the posterior portions of the cerebral 

 hemispheres, and the optic lobes are clearly seen to have become 

 pushed out laterally, and pressed down vent rally. 



In the lateral view the optic lobes will be seen to have 

 descended considerably : they are moving forward vent rally as 

 well as downwards. The cerebellum is well developed on the 



