140 CARL RICHARD MOORE. 



development if subsequently treated with sperm, provided only 

 that the membranes are destroyed sufficiently to allow sperm to 

 reach the eggs. In his opinion only those physical factors that 

 may prevent sperm from coming in contact with the egg are 

 concerned in the non-fertilizable character of eggs possessing 

 distinct membranes. 



His views aie then entirely at variance with the idea that 

 the egg bears its own fertilizing substance which is set in motion 

 by activating agents, spermatozoa or artificial agents, and that 

 once this activation has been effected no repetition of the same 

 is possible. He leaves out of account any physiological change 

 in the protoplasm of the egg and bases his entire conception 

 upon purely physical factors at the boundary of the egg. 



A more thorough analysis of the physiological conditions 

 within the egg, following activation by any means, is highly 

 desirable whatever theory we may be inclined to favor. One 

 method of attack of such a problem is a more thorough study 

 of the possibilities of a combination of parthenogenesis and 

 fertilization. Certain observations have already been inci- 

 dentally presented from this point of view. 



Loeb ('13) finds that eggs of the sea urchin may be readily 

 fertilized after membrane production if only the membranes 

 are torn by shaking the eggs and sperm is added. 



Herbst ('06) fertilized Sphcerechinus eggs, having been previ- 

 ously treated with 50 c.c. sea water + 3 c.c. n/io acetic acid for 

 two to six minutes, with Strongylocentrotus sperm and obtained 

 larvae bearing predominant characters of the female parent. In 

 the fertilization process membranes were not produced, cleavage 

 was very abnormal, and resulting plutei were weak: there was 

 usually a high degree of mortality in his cultures. 



Tennent and Hogue ('06) were able to fertilize starfish eggs 

 for a short time only, following membrane production induced 

 by CO 2 : according to their account sperm swam through the 

 enlarged vitelline membrane entered the egg and caused the 

 production of a second membrane. 



Lillie ('14) calls attention to his observations that eggs of the 

 sea uichin following membrane production are incapable of being 

 fertilized. 



