THE CATALYST ENTELECHY IN DIFFERENTIATION 211 



which furnish small quantities of essential substances, or the 

 failure of the plants or animals furnishing such substances to 

 produce them in sufficient quantity." 



V. L. Colucci 66 and G. Wolff' 37 independently reported that, on 

 removal of the lens from a larval or an adult amphibian, a new 

 lens develops from the upper margin of the iris. Recent ex- 

 periments with this "Wolffian regeneration" showed that if small 

 bits of iris are snipped off and pushed into the eye-chamber 

 (corpus vitreum), lenses develop there; but bits of ectoderm acted 

 likewise. With Rana esculenta Wolffian regeneration fails in the 

 presence of a normal lens, but if the lens is removed, lenses form 

 on implantation into the eye of neural plate tissue, ectoderm, 

 eye-cup, somite mesoderm and ear vesicle. Tissue cultures of chick 

 iris are reported to have produced lenses. It might well be that 

 the eye-chamber can supply specific prosthetic material, while the 

 other diverse tissues supply the specific carrier material, or vice 

 versa. 



The secondary organizers responsible for lens formation are 

 stable enough to stand boiling, and like primary organizer they 

 seem to be present in all tissues. But the amount is limited 

 locally, for on repeated extirpation and regeneration the third 

 lens in the series was poorly developed, and no fourth lens ap- 

 peared. Prolonged rest restored the regenerative power; either 

 the active substance had been reformed locally, or else the widely 

 distributed organizer had diffused in. If the latter possibility is 

 true, it would be evidence in favor of the view advanced by J. 

 Alexander 68 as to how the gametes (ovum and sperm) receive the 

 enormous number and variety of particulate units which are 

 needed to form, or to serve as templates for forming the specific 

 catalysts, prosthetic groups or carriers needed to carry out the 

 material catalyst entelechy. Alexander stated: "How can heritable 

 factors, apart from genie or chromosomal changes, enter into and 

 affect the cells which carry heredity? 



"It is reasonable to believe that the cytoplasm of germ cells, 

 like that of other cells, tends to receive an average supply of the 

 molecular flotsam and jetsam, that is, of all particulate units 

 which are carried throughout the body by circulation and diffu- 

 sion, and that among these molecular or near molecular units 

 are those that determine or aid in determining, differentiation. 

 Apart from other evidence, the fact that some differentiated cells 

 can breed true in tissue culture warrants the belief that specific 



