190 



In section number 26 there is a stage in which the closing lens 

 seems to be in the act of cutting the sac otf. This could only be 

 proven by making sections at right angle to the visual axis of the eye 

 and seeing if the pedicle of the sac were incorporated in the lens tissue. 



The study of this embryo leads to several considerations. Firstly : 

 Whether the early accidental escape of the liquor amnii from the con- 

 cavity of the lens allowed the amnion to fall in. Secondly: Whether 

 the inner layer of the amnion, being torn, allowed the liquor amnii to 

 flow between its two layers producing an hydrops and thus crowding 

 the ectodermal layer of the amnion into the lens-vesicle. On some of 

 the sections lower down distinct tears coud be made out in the inner 

 layer of the amnion thus accounting for the above supposition. 



> 



^^^, 



as^. 



I Lens vesicle, a A portion of a fold of amnion, b Mesodermal and c ecto- 

 dermal layers of another fold of amnion. 



Thirdly: Could the excessive accumulation of yolk masses, over 

 this area, have contributed to produce the protrusion? 



The ultimate effect of this tissue must be a matter of speculation ; 

 it may have been cut ofi' and then remained in the lens -vesicle be- 

 coming organized and disturbing the nutrition of the lens or it may 

 have been absorbed like the cells which are cast off from the wall of 

 the lens-vesicle. This conjecture is improbable because of the foreign 

 character of the cells of the amnion which would have acted detri- 

 mentally to the normal development and nutrition of the lens. 



It is also possible that the protrusion may have been withdrawn 

 later. 



The dipping in of the amnion took place either before the egg 

 was opened or after the egg was opened. The evidence in favor of 

 the first theory is, that in section number 26 the amnion seems in 



