422 E. I. WERBER 



morphogenetic factor — blastolysis — is apparently responsible for 

 both the 'monstra per defectum' and the double monsters and 

 other 'monstra per excessum.' 



The next example which we have chosen for the demon stra- 

 tion of the apparent syngenesis of both these deviations from 

 the norm may now follow. 



In figure 12 is presented an egg with a large 'pericardial' 

 vesicle, dense vascularization of the yolk-sac and a very curi- 

 ously misshapen embryonic mass which in toto was with some 

 doubt interpreted as a dwarfed and highly malformed double 

 monster. Microscopic examination of sections fully confirms 

 this interpretation. 



The first sections pass through the anterior part of the larger 

 component only. They show (fig. 23) a dissociated tissue of 

 an indifferent character in which are embedded two lenses, I and 

 li. Further sections show that this tissue mass increases in 

 density posteriorly and that it is the anterior, greatly dissoci- 

 ated, part of the single optic cup which 'eventually comes fully 

 into view surrounding on all sides the larger one of the two 

 lenses (fig. 24). The brain of this component is unilobed, very 

 irregular in shape and unusually small, while the eye is very 

 large. The unusual shape of the latter (fig. 25) as well as also 

 the fact that the ill-differentiated layer of rods and cones does 

 not (as it should) appear throughout the entire outer margin 

 of the optic cup wall, but is observed for a considerable stretch to 

 merge into the other layers of the retina, suggests that the eye 

 has been formed out of a dissociated anlage. The above men- 

 tioned dissociated optic tissue mass anterior to the eye adds 

 considerable weight to this evidence of blastolytic action. 



The smaller component appears first in the twelfth transverse 

 section. It is also possessed of one eye only which is rather 

 small anteriorly and very irregular in shape. In more posterior 

 sections, however, this optic cup gradually increases to an un- 

 usually large size, (o.c, fig. 26) it being almost as large as the 

 brain of the component. The latter is unilobed, very irregular 

 in shape and relatively very large. 



