LIFE CYCLE OF SIMOCKI'I I \l I S VETULUS. 



6 7 



become asexual. After the production of several ephippia a 

 partial one may be developed as the female leaves the sexual 

 state, or she may change over abruptly. The degrees of sexu- 

 ality are infinite, since it is subject to continuous and not to 

 integral variation. 



Considering the stem mothers from the standpoint of size 

 attained, viability, length of life, activity, etc., in the first few 

 generations of offspring, in addition to the proportion of the kinds 

 of offspring as to sex, and the degree of sexuality of the females, 

 one is forced to conclude that stem mothers are not functionally 

 at all unlike the females which are produced parthenogenetically, 

 with the exception that not a single instance of the production of 

 an ephippial egg by a stem mother has been noted. This last 

 is in strict accordance with the findings of Grosvenor and Smith 

 (1913) for the stem mothers of Moina rectirostris, and of most 

 writers, though rarely instances of the contrary are noted, e.g., 

 Scharfenberg (1911, p. 24). 



The most important data are excerpted from the tabulated 

 summary of experiment 3 and slightly rearranged in the following 

 table for the convenience of the reader. 



Experiment 4. Temperature experiments with Simocephalus 

 yield very indefinite results. Individuals do not thrive at a 

 higher temperature than 28 C. Even at this temperature 

 isolated individuals live only a short time. Several experiments 

 designed to test the effect of high temperature were performed 

 in the following manner. Specimens were taken from laboratory 

 cultures and placed in glass containers having loose covers to 



