532 E. I. WERBER 



the sustained injury is of a still higher degree, i.e., if only a 

 fragment of one optic anlage survives, the cyclopean or asym- 

 metrically monophthalmic eye, formed from it, will be of a corre- 

 spondingly small size. And, finally, if the entire ophthplmo- 

 blastic material is destroyed by the blastolytic process, the 

 defect will result in anophthalmia vera. 



At this point it should be noted that there is yet another kind 

 of anophthalmia, which is not due to blastolytic destruction but 

 apparently to an inhibition. In anophthalmic embryos of the 

 latter category there are always found on microscopic examina- 

 tion eyes which owing to the exhaustion of their chemomorphic 

 capacity, have remained at a very early stage of development 

 (figs. 23 and 24, p. 494 and fig. 49, p. 520). This, however, is, I 

 believe, the only instance where an ophthalmic deformity is due 

 to inhibition, while all synophthalmic and one-eyed conditions 

 owe their origin to a defect brought about by blastolytic 

 elimination. 



For a better understanding of the morphogenesis of ophthalmic 

 terata it is also necessary to consider the time at which blastoly- 

 sis brings about the changes leading to their formation. Since it 

 can be shown that in Fundulus eggs under the influence of toxic 

 solutions the chemical injury follows the rule of the 'axial gradi- 

 ent,' i.e., it proceeds from the anterior end posteriorwards, it 

 seems safe to assume that the blastolytic lesion is sustained at a 

 very early, primitive stage of development, long before differen- 

 tiation of organs has yet begun. 



In a previous paper (Werber '15 c, p. 558) I have advanced 

 the view that the blastolytic injury is sustained before the for- 

 mation of the embryonic shield. To be more precise, it may 

 be said that this elimination of destroyed material most likely 

 occurs at a late 'Randwulst' -stage of the germ-ring. For it is 

 at this stage that very important events take place which eventu- 

 ally lead to the organization of the embryonic body and differen- 

 tiation of tissues and organs. At that time of transformation 

 of the blastoderm into the embryo which is accompanied by 

 rather active movements or shiftings of the embryo-forming 

 material, the contact between the sound, unaltered part of the 



