FERTILIZATION REACTION IN ARBACIA PUNCTULATA. 267 



Table V6. 



Drops of 1 • 25 Sperm Per Cent. Per Cent. 



Suspension. Membranes. 1st Cleavage. 



I o o 



2 O O 



4 2 narrow. o 



8 70 " 0.5 irregular. 



12 80 " o 



16..... 100 " 1 



Inseminated control in sea-water 100 good. 100 



Uninseminated control in sea-water o o 



Effect of increased sperm concentration in immediate insemination in 1 : 11,111 

 PtCU. June 30, 1922. Eggs as in Table Va. Exp. 10 : 00 A.M. Temp. 21 C. 



increased sperm concentration shows the resistance of this solu- 

 tion to enforced insemination as well. Only after the eggs have 

 been left in normal sea-water for four minutes after insemination 

 therein, does the viability in Table Va begin to approach the 

 normal control. At this same concentration, I : n,ni, while 

 100 per cent, membrane elevation may be produced by increase 

 of the sperm concentration from one to sixteen drops of the 

 1 : 25 suspension, only i per cent, of the eggs cleave and these 

 are irregular. 



Table Vc. 



Time of Transfer 

 after Insemination in Per Cent. Per Cent. 



Normal Sea-water. 2 Cell. 4 Cell. 



10 min o o 



20 " o 



30 " , o o 



45 " 2 



Inseminated control in sea-water 96 96 



Viability test in 1 : 1,945 PtCU. July 1, 1922. Eggs 2 : 00 P.M. Sperm 

 fresh. Insemination 1 : 25 : 7.5. Membranes 100 per cent. Experiment 3 : 30 

 P.M. Temp. 22 C. 



A test of the cleavage-toxic point gave that determination as 

 1 : 1945. As soon as the eggs were transferred to such a solution 

 after insemination in normal sea-water, they become crenate. 

 Such a solution allowed no cleavage up to 45 minutes when the 

 eggs were transferred to it at intervals after insemination in 

 normal sea-water. The results of this experiment are given in 

 Table Vc. Cleavage took place in 48 minutes in the controls. 



7. Lead Chloride. — PbCl 2 , when added to sea-water precipitates 

 very freely. This precipitate is not so heavy, however, that the 

 membrane-inhibiting concentration cannot be determined as 

 1 : 4,000 or iV/554 (p.H. 7.0.). Some precipitate was present 



