THE PROBLEM OF ACTIVATION 231 



tinating substance, but in such cases the spermatozoon 

 exerts no fertilizing action whatsoever. Thus unripe 

 eggs of the sea urchin, which contain no agglutinating 

 substance, may be entered by spermatozoa if high con- 

 centrations of sperm are used, but no change results in 

 the egg, and the sperm heads remain entirely unchanged 

 within the cytoplasm. The same phenomenon may be 

 observed, as described by Moore (1916), in the case of 

 eggs treated for the optimum length of time for pro- 

 duction of parthenogenesis by butyric acid; these eggs 

 are devoid of agglutinating substance, but after removal 

 of the membranes they may be entered by numerous 

 spermatozoa, which are perfectly inert in the egg cyto- 

 plasm; nor do the eggs react as would be expected if 

 the sperm carried a " fertilizing substance." 



These facts do not, however, definitely prove that 

 the agglutinating substance is the activating substance 

 of the egg, but they at least show that there is a parallel 

 between absence or loss of agglutinating substance and 

 the capacity of the egg for being activated. The same 

 results would be attained if there were two substances 

 concerned, viz., an agglutinating substance and an 

 activating substance, which were produced or lost 

 simultaneously and which interact in the process of 

 fertilization. This is, as I understand it, substantially 

 the position taken by Miss Woodward in her recent 

 study (1918); but since the two effects, the sperm- 

 agglutinating and the egg-activating, appear and dis- 

 appear together in these instances, the writer assumed 

 that they may be regarded as due to a single complex 

 substance, for which the name "fertilizin" appeared 

 appropriate. 



