534 



E. I. WERBER 



lowing a suggestion made by Schwalbe and Josephy ('13, p. 205- 

 206) I have attempted to portray this elimination diagrammati- 

 cally, employing Kopsch's diagram as a basis (fig. 50). 



In the dotted area K, which is the primordium of the head, 

 the two horizontally barred circles represent groups of cells 

 which would normally develop into the mouth and olfactory 

 pits, while the two cross-barred circles immediatel}^ below repre- 

 sent the ophthalmoblastic material of both sides. If it now be 

 imagined that blastolysis has eliminated a wedge of tissue which 



Fig. 50 Diagram of germ-ring with thickened embryo-formating areaCKein;- 

 randwulst') — modified from Kopsch. 



Fig. 51 Diagram of the early steps in the formation of the enilnyo from the 

 thickened area of the germ-ring (from Kopsch). 



as seen in the diagram, is directed with its point posteriorly, 

 while it is broadest anteriorly, this wedge would contain, more 

 or less, the potential interocular area, parts of the potential 

 mouth and the potential olfactory pits of both sides. A con- 

 siderable part of the potential forebrain would in this way also 

 be eliminated. The gap thus resulting will soon close, owing to 

 a contraction brought about by the elongation which accom- 

 panies the transformation of the head primordium of this stage 

 into the head. What would be the final result of the elimination 

 of such a wedge of tissue and the subsequent closure of the 

 wound? A glance at figure 50 would show that the potential 



