362 E. I. WERBER 



to imagine that some free lentoids found in such embryos may 

 owe their origin to heteromorphosis from dispersed optic cup 

 fragments. However, it seems doubtful whether fully differ- 

 entiated free lenses of large size originate from this source. 



While, of course, this possibility cannot be entirely disregarded, 

 the evidence points to the conclusion that the fully differentiated 

 free lenses found in some teratophthalmic embryos are due to a 

 chemical stimulus of blastolyzed potential optic cup substance 

 on any part of the ectoderm with which it may chance to come 

 into contact. It is quite possible that this stimulus (the lento- 

 genic reaction) is in the nature of a catalytic reaction such as 

 was assumed by Herbst ('01) to underlie the differentiation of 

 the secondary sexual characters owing to products of internal 

 secretion of the sex glands. 



Reactions of this nature (autocatalysis) have in recent years 

 been assumed by J. Loeb ('02, '09), Robertson ('08) and Hage- 

 doorn ('11) and others to underlie the mechanisms of develop- 

 ment, growth and inheritance. According to Hagedoorn the 

 hereditary (genetic) factors are to be regarded as autocatalytic 

 substances. A similar view has been advanced recently also by 

 Goldschmidt ('16) who pointed out a quantitative analogy be- 

 tween genetic factors and enzyme reactions in the inheritance of 

 wing pigmentation by various moth hybrids of a known gametic 

 constitution. 



The significance of these views is obvious. For, if their cor- 

 rectness should be established, we should gain a very deep in- 

 sight into the governing forces of development. The evidence 

 will be the more valuable if it is furnished by both genetics and 

 experimental embryology. One instance of such evidence will, 

 I think, eventually be found to be presented by the mode of 

 origin of the lens in vertebrates. 



MARCH 29, 1916 



