86 K. K. Oliver: 



In the lateral view (6a) the curved surface of the cerebral 

 hemispheres can be seen to have become more prominent dor- 

 sally than the optic lobes, which are now so far pushed laterally 

 and ventrally that the chiasma and infundibulum are scarcely 

 seen. The lobes have assumed a definite oval shape at this 

 stage. The cerebellum has developed considerably, there now 

 being eight convolutions visible from the lateral aspect. The 

 floeculi, too, are taking definite form, while the medulla has 

 increased in size, and is in proportion to the rest of the brain. 



6c (Fig. 6, Section 1) shows the most anterior portion of the 

 optic lobes, but so far forward that there is no optocoele in- 

 cluded, and ventrally the chiasma has been cut through. 



In 6d (Fig. 6, Section 2) a section about the centre of the 

 lobes is given, showing the connection of the optocoele with the 

 other brain cavities. 



6e (Fig. 6, Section 3) cuts through the posterior portion of 

 the optic lobes and the anterior convolution of the cerebellum. 



Stage VII. (Plate XXXI.) 



The seventh stage corresponds approximately to a period of 14 

 days' incubation. 



In dorsal aspect the cerebral hemispheres are seen to have 

 become roughly triangular, and are increasing in size at a pro- 

 portionately greater rate than the optic lobes (7b). The epiphysis 

 is now closely surrounded by the cerebral hemispheres anteriorly, 

 and the optic lobes posteriorly. The optic lobes have quite lost 

 their dorsal prominence, and are now lateral structures. The 

 cerebellum has increased greatly both in size and in the definite 

 formation of its convolutions, there being now eight definite 

 convolutions visible on the dorsal aspect. The ninth, and 

 originally the most posterior convolution, is hidden underneath 

 the one anterior to it, in earlier development, though now, 

 through the curling back of the cerebellum, posteriorly placed. 

 The medulla is much as in the last stage, but the development 

 of the cerebellum has partially hidden it. 



In 7a the cerebral hemispheres can be seen to be becoming 

 more developed. The ventro-lateral depressions are clearly 

 marked. The optic lobes have altered but little since the pre- 



