520 E. I. WERBER 



into two and in the small size of the other eye due to destruc- 

 tion of a part of the potential eye anlage of this side. The 

 injury sustained was a rather severe one for it affected also the 

 brain, the bilaterality of which is obscured (as seen in fig. 80), 

 and the rest of the body. However, it is at the anterior end of 

 the embryo's body where most damage seems to have resulted 

 from the process of destructive dissociation (blastolysis) . 



The general defects are usually even more extreme in embryos 

 in which on examination in toto only a small rudiment of an 

 eye, like a fragment of the pigment epithelium, is found, or where 

 no eyes at all can be detected (cf. figs. 23 and 24). As a rule, 



Fig. 49 Camera lucida drawing of a transverse section through the head of 

 the embryo in figure 23. o.c, optic cup; I., lens; br., brain; e.v., ear vesicle. 

 X 125. 



it is found on microscopic examination of sections that most 

 anophthalmic embryos possess poorly differentiated and deeply 

 buried eye anlagen, sometimes with a profusion of very small 

 lenses. In figure 49, which is a transverse section through the 

 anterior head region of the embryo in figure 23, two optic vesicles 

 of unequal size can be seen with lenses of corresponding sizes. 

 The simultaneous appearance in the same section of a rudimen- 

 tary ear vesicle, the unequal size and proximity to each other 

 of the rudimentary optic cups as well as the distortion of the 

 brain would seem to well warrant the assumption of blastolysis 

 as the morphogenetic factor responsible for the defects of this 

 embryo. 



