248 



PROBLEMS OF FERTILIZATION 



the percentage of eggs developing to larvae may be 

 as high by heat parthenogenesis as by fertilization, for 



31 C. THREE EXPERIMENTS 



32 C. SIX EXPERIMENTS 



DURA- 

 TION OF 

 EXPO- 



PERCENTAGES OF EGGS FORMING FREE-SWIMMING LARVAE 



it is rare to secure 80-90 per cent developing larvae 

 by fertilization with this material. (2) A short expo- 

 sure may cause membrane formation with no subse- 



