358 E. I. WERBER 



sary to compare it with sections through the anterior part of 

 the eyes where areas of such disintegration and interminghng of 

 'naked' nuclei of the same two types are also found, to disarm 

 any skepticism on this point. 



If, however, it is granted that the tissue mass in question is 

 retina, the origin of the lentoids of this region as well as in the 

 most anterior part of the embryo can no longer be doubted as 

 due to contact of ectoderm with dispersed particles of ophthal- 

 moblastic substance. Blastolysis has in this way affected also 

 the brain, which besides its unusual distortions also exhibits dis- 

 tinct traces of disintegration. Part of the cartilaginous roof of 

 the mouth in this region is also lacking and it is this part that 

 is filled with disintegrated retina. If the sections be followed 

 caudalwards the roof of the oral cavity is observed to appear 

 gradually more and more complete until a section is reached 

 where the defect no longer exists. At this level, no more disin- 

 tegrated retina is found in the mouth, but imbedded in the oral 

 epithelium a number of lentoids can be observed in six sections 

 (fig. 7). Beyond this level the epithelium of the corresponding 

 part of the oral cavity consists in several sections of large vesic- 

 ular cells which look decidedly as if they were in a stage inter^ 

 mediate between the epithelial and early lentoid. Of all the 

 evidence for the blastolytic origin of the lentoids of this embryo 

 presented so far, the lentoids of the oral cavity form, I believe, 

 the most striking if not the most important, part. For here the 

 lentogenic reaction (as I would term it) of ectodermal epithelium 

 to optic cup substance is demonstrated in a manner, which would 

 seem to leave no room for reasonable doubt. 



Not less obvious is the conclusion to which these observations 

 would seem to lead. The free lenses of teratophthalmic em- 

 bryos recorded by Stockard, Mencl and myself, are not inde- 

 pendent in their differentiation, but due to a specific (catalytic?) 

 reaction of dispersed fragments of optic cup substance on the 

 ectoderm with which they may chance to come in contact. 



Mend's and Stockard's observations regarding the free lenses 

 in teratophthalmic embryos which seemed to form such impor- 

 tant evidence against Herbst's* theory of the developmental cor- 



