FERTILIZATION AFTER INITIATION OF DEVELOPMENT. 291 



Miss Allyn ('12) found that any substance that had a tendency 

 to initiate development in Clicetopterus was detrimental to 

 fertilization. She noted that the tendency was not for the 

 exclusion of spermatozoa but rather for the production of poly- 

 spermy. The aberrant type of cleavage became more accentu- 

 ated as the exposure to the initiatory agent was prolonged and 

 would probably have entirely prevented fertilization with a 

 slightly longer exposure. In this case the initiatory agents 

 induced only a partial completeness of the reactions and as time 

 went on fertilization became less and less possible, indicating the 

 gradual loss of some substance w r hose presence is indispensable 

 for fertilization. Arbacia eggs behave in essentially the same 

 manner if over-exposed to butyric acid; polyspermy appears if 

 insemination is carried out shortly after the exposure, but if the 

 eggs remain standing in sea-water for a few hours insemination 

 has no effect. 



Just how hypertonic sea-water is effective we are not able to 

 say, but the writer is inclined to the views of R. S. Lillie that a 

 properly timed exposure to any substance that lowers permea- 

 bility (unless it be decidedly toxic) allows of the combination of 

 the substances within the egg that starts off the developmental 

 reactions. If these changes are nearly enough the normal, 

 development is quite complete up to certain stages in the life 

 of the organism. The question, however, to which these experi- 

 ments relate is the capacity for fertilization after activation by 

 hypertonic sea-water. 



The quantitative reaction idea has been pointed out quite 

 freely in this and a preceding paper in considering the initiation 

 of development, and certain instances of all phases of this process 

 are to be had not only from the experiments themselves but also 

 from the preserved material. From the purely parthenogenetic 

 standpoint the ideas of the qualitative specificity of hypertonic 

 sea-water as a factor in the initiation of development have been 

 dealt a death blow by the experiments of R. S. Lillie ('15) on 

 starfish eggs, and the purely quantitative idea substituted for 

 the explanation. Lillie finds that not only can starfish develop- 

 ment be initiated by a preliminary treatment with butyric acid 

 followed by hypertonic sea-water, but also that a secondary 



