LIFE CYCLE OF SIMOCKI'HALIS VETULUS. 



perfectly fresh, and could hardly have been imhulrlu-d eggs of 

 the- preceding season. That they were Simocephalus eggs is 

 quite certain since the only other Daphnian of similar size in 

 these ponds is Daphnia pulex, whose ephippia contain two eggs 

 each. 



That the practical freedom from sexual forms in this instance 

 is clue to external conditions is rendered absolutely certain by 

 the fact that these same females when the jars were placed in 

 the laboratory and the water no longer regularly changed, begun 

 to produce males and sexual females, in just about the same 

 proportions as in experiment 3 and 4, as nearly as could be judged 

 from general observation. 



TABULATED SUMMARY OF EXPERIMENT 5. 



V. EXPERIMENTS WITH EPHIPPIAL EGGS. 



Authors are not agreed as to the factors involved in shorten- 

 ing the latent period of the ephippial egg. Experimentation 

 along this line has yielded the most inconsistent results. *I have 

 repeated the experiments of Weismann and others of freezing 

 the eggs for varying lengths of time with all but complete failure. 

 Hence I shall give in detail the experiments I have performed in 



