352 E. I. WEEBER 



of ophthalmoblastic material which sometimes develop into frag- 

 ments of an optic cup. I have observed several such instances 

 and have always found that the relation between such a tera- 

 toma and the terata of the eyes in the same embryo is clearly one 

 of syngenesis. In several of such embryos free lenses were found 

 which were located far away from an eye or optic cup fragment. 



These observations which fully agree with Stockard's ('09, 

 '10) and Mend's ('08) findings,^ and the fact mentioned above 

 that free lenses occur only in teratophthalmic embryos suggested 

 that the origin of such lenses is in some causal connection with 

 blastolysis. The dispersion of ophthalmoblastic material and 

 the simultaneous presence of free lenses in some teratophthalmic 

 embryos suggested strongly that the origin of the latter depends 

 upon the former. While examining sections of many terato- 

 phthalmic embryos during the winter of 1915 this hypothesis 

 forced itself upon me by the sheer weight of the remarkable con- 

 currence of facts, which could not, by any means, be considered, 

 as fortuitous. For, why do free lenses arise only in such cases 

 where the eyes are defective as a result of blastolysis, that is, 

 where ophthalmoblastic substance has been partly destroyed, 

 and partly dissociated or dispersed? 



These considerations have, finally, led me to the following 

 theoretical conclusion which I regard as a possible basis for more 

 refined experiments towards the solution of the lens-problem: 



It could be imagined, I thought, that just as in normal de- 

 velopment two lateral lenses arise as the result of an apparent 

 contact stimulus from two lateral optic cups and just as in the 

 Cyclopean eye one median lens arises as a result also of a con- 

 tact stimulus of one median eye, the free lenses of teratophthal- 

 mic embryos could arise from indifferent ectoderm owing to a 

 stimulus from a fragment of ophthalmoblastic material too small 

 to differentiate in the state of its isolation into a morphologically 

 discernible structure. This stimulus is, as Herbst (I.e.) has 

 pointed out, not a contact stimulus only, but very probably a 

 specific thigmomorphosis, the mechanism of which I am inclined 



2 Cf. Stockard ('09, fig. 45, p. 317 and '10, figs. 6 and 8, p. 403 and figs. 22, 23, 

 24, p. 409) and Mencl ('08, plate xx, figs. 5, 6, 7, and 8). 



