486 ALVALYN E. WOODWARD 



lizin,'" which, m turn, causes cleavage. Such an activation of 

 fertihzin might be conceived as an increase in the affinity of the 

 ovophile group for the egg receptor (Glaser). Tliis hypothesis 

 seems difficult to confirm. How are we to get rid of the sperm 

 in a sperm-fertilizin mixture without injuring the fertilizin? 

 Sperm pass readily through any available filter through which 

 fertilizin can pass, but can be killed by heating to 40°C. for three 

 minutes. Since fertilizin does not lose its ability to agglutinate 

 sperm if boiled for a few minutes, a method suggests itself,^ 



Equal amounts of Arbacia fertilizin were put* into two test- 

 tubes and to one was added a large amount of Arbacia sperm. 

 They were allow^ed to stand fifteen minutes, then both tubes were 



TABLE 13 



A comparison of the parthenogenetic effects of fertilizin with those of fertilizin 



'activated' Ijy sperm 



1. Eggs (Control 1) 



2. Eggs + fresh sperm (control 2) 



3. Eggs + heated fertilizin (diluted to ^) 2 hours + hypertonic 20 min. 



4. Eggs + heated fertilizin (diluted to i) 2 hours 



5. Eggs + heated mixture of fertilizin and sperm (diluted to H) 2 hours 



6. Eggs + heated fertilizin (diluted to \) 2 hours 



7. Eggs + heated mixture of fertilizin and sperm (diluted to I) 2 hours 



PER CENT 

 CLEAVAGES 







70.5 



61 



22 



21 











heated in a water-bath to 40°C. for three minutes. Eggs were 

 then treated as in table 13. In experiment 4 and those following, 

 hypertonic after-treatment was not given, since that in itself 

 causes development in some cases, and I wished to learn the effect 

 of the 'activated fertilizin.' Dilutions w^ere used because it was 

 thought that they might show more clearly the greater activity 

 of fertilizin mixed with sperm. Repetition of this experiment 

 gave essentially the same results. 



Since the heated fertilizin alone caused development in 22 per 

 cent of the eggs and that to which sperm had been added caused 



^ Glaser first attempted to solve this problem, but failed because he boilfed the 

 mixture of sperm and fertilizin, and thus, obtained 'purple x,' which inhibited 

 development. 



