240 PROBLEMS OF FERTILIZATION 



in these effects, and she has worked out a theory 

 of the activating effect which is entirely original. 

 This theory does not explain why the sperm- 

 agglutinating and the egg-activating properties of egg 

 secretion always go together, as Miss Woodward has 

 herself emphasized in various places in her paper; 

 when the egg ceases to produce the sperm-agglutinat- 

 ing substance it has lost its capacity to be activated. 

 These two properties of the egg secretion hang together 

 normally; their separation under the conditions of 

 chemical analysis may possibly denote a splitting of a 

 single substance of the normal egg. 



II. EXPERIMENTAL PARTHENOGENESIS 



The determination of the existence of a substance 

 in the egg necessary to fertilization obviously does not 

 show in what way activation results.. We shall there- 

 fore consider the problem of activation from the point 

 of view of experiments in parthenogenesis, often too 

 hopefully called the physicochemical standpoint. The 

 books of Loeb (1913) and Delage and Goldsmith (1913) 

 treat this subject in detail. We shall confine ourselves 

 to certain outstanding facts and theories of experimental 

 parthenogenesis. In considering these it should be 

 borne in mind that, though the number of forms in 

 which parthenogenesis has been experimentally induced 

 is large, in another considerable number of forms suc- 

 cessful methods have not been found; e. g., in the entire 

 vertebrate phylum, with the single exception of the frog. 

 This may be due to secondary conditions of the problem 

 in such cases, or it may be due to failure to reach a 

 correct analysis of the successful results. 



