234 E - I - WERBER. 



All of these deformities are thus clearly due to a defect (or defects') 

 of a blastolytic nature. Not only is this the case in experiments in 

 which the modification of the environment employed is a chemical 

 one, but also, if a physical, e. g., thermic, modification be em- 

 ployed. For, in experiments (not yet published), in which the 

 eggs of Fundulus heteroclitus were subjected to the action of a 

 temperature much below the normal, some terata and partic- 

 ularly ophthalmic monsters resulted. The latter are due to loss 

 at an early embryonic stage of parts of ophthalmoblastic material 

 and to like damage sustained by the anterior part of the potential 

 head. Thus anophthalmia results from such loss by the earliest 

 brain primordium of the whole or nearly whole ophthalmoblastic 

 material. 



In some anophthalmic embryos such blastolytic optic-cup frag- 

 ments or even small, fairly well differentiated optic-cups may on 

 microscopic examination of sections be observed either enclosed in 

 the brain between both hemispheres (intracerebral cyclopia, as it 

 were, cf. Mencl '08, Figs. 2 and 3) or in a lateral position as a part 

 of the brain. Such "concealed" remnants of the optic cup may 

 often lack the tapetum nigrum and the histological character of 

 retina, owing to early destruction of some groups of cells which 

 potentially corresponded to the lacking layers of the retina, and 

 may thus give the appearance of a part of the brain. If it happens 

 to come into contact with the epidermis, such "a part of the 

 brain" will stimulate the differentiation of a lens from it. 



This, undoubtedly, is exactly the condition in the case described 

 by Mencl in 1903. I have many times observed unmistakable 

 optic cups which lacked some of the histological characteristics 

 of retina and whose structure was very much like that part of 

 the "brain" in Mend's case (cf. Mencl '03, Figs. 2, 4 and 5, and 

 also '08, Fig. i), into which the larger one of the two lenses has, 

 as it were, burrowed in. That part of the "brain " is undoubtedly 

 a "verkappte" retina, as Spemann had once suggested. 



This, I think, disposes of the first, but most troublesome, case 

 described by Mencl. It might perhaps be added that the asym- 

 metric position of the two lenses 1 in the head of this anophthal- 



ll 'Die linke liegt mehr dorsal und zugleich caudalwarts von der rechten" 

 (Mencl, '03, p. 331). 



