LIFE CYCLE OF SIMOCKl'IIALUS VKTTLrs. <)I 



as evidence that the female producing them is undergoing transi- 

 tion from male producing to female producing or vice versa. 



3. The production of ephippia and ephippial eggs are related 

 but not causally, both being dependent upon common internal 

 factors. The introduction of males into a culture does not in- 

 duce the production of ephippial eggs, nor docs their presence 

 have any relation to the prolongation of the sexual state when it 



has once appeared. 



II. Breeding Habits. 



Sexual attraction is limited not only to sexual females in the 

 sexual state, but is confined to a limited period of a few hours 

 before the ephippial egg is laid. It seems to be due to some kind 

 of substance omitted by the female and borne by her exhalant 

 respiratory current, where it is detected through a chemical 

 sense by the male. Fertilization seems to take place in the 

 brood pouch after the egg is laid. The presence of the spermato- 

 zoa in the brood chamber is probably the stimulus for its extru- 

 sion. In the absence of fertilization the ephippial eggs are usually 

 resorbed in the ovary, or, if laid they undergo degeneration in 

 the ephippium within one or two days. 



III. Theoretical. 



The immediate significance of the ephippial egg is as a stage 

 in the life cycle resistant to adverse conditions, and not in the 

 stem mother hatching from it, since her offspring are in no way 

 unique. A more remote but more fundamental significance, 

 held in common of course, with all fertilized eggs and zygotes, 

 is that it provides for the permanent lability of the species 

 through amphimixis. In view of the great prolificacy of the 

 species in regard to all of its forms, and the almost universally 

 concomitant occurrence of males and sexual females, the develop- 

 ment of only I per cent, of the ephippial eggs would be quite 

 sufficient to secure to the species all of the benefits to be derived 

 from their two functions. It seems probable that there is a 

 very great inherent variability in the capacity for development ol 

 the ephippial eggs in a state of nature, and the lack of uniformity 

 of results obtained by the various investigators in their attempt- 

 to shorten the latent period may be explainable on that basis. 



