APP.] EMBRYO OF THE THIRD DAY. 253 



G Removal of the embryo from the yolk, as in 



II. C. 



D. Surface view of the transparent embryo from 



above. 



Notice : — 



1. General form of the embryo. 

 a. Commencing cranial flexure. 

 h. The tail and side folds. 



2. Amnion. Notice the inner and outer (false amnion) 

 limbs and remove them with a needle. When the 

 amnion has been removed the features of the 

 embryo will be much more clearly visible. 



3. The organs of sense. 



a. Eye. Formation of the lens already nearly 

 completed. 



h. Auditory involution, now a deep sac with a 

 narrow opening to the exterior. 



4. The brain. 



a. The vesicles of the fore-, mid-, and AmcZ-brain. 



b. The two cerebral lobes, which have been budded 

 off from the fore-brain. 



c. The cranial flexure taking place at the mid- 

 brain. 



E. Transparent embryo from below. 

 Manipulation as in II. E. 



Notice : — 



1. The increase of the head-folds of the somatopleiire 

 and splanchnopleure, especially the latter, and the 

 commencement of these folds at the tail. 



