FERTILIZATION REACTION IN ARBACIA PUNCTULATA. 265 



5. Aluminium Chloride. — The tests with A1C1 3 were much like 

 those for the metals already described. The results were also 

 much the same. It was found that a concentration of 1 : 40,000 

 (p.H. 7.2) would completely inhibit membrane elevation and 

 that a concentration of 1 : 10,000 (p.H. of less than 6.6) was 

 toxic to cleavage when the eggs were transferred to it after 

 insemination in normal sea-water. As in the case of LaCl 3 , the 

 sperm were clumped when added to the solution, but when 

 NaOH or egg sea- water was added, this clumping was corrected 

 and the sperm became active. < When the egg sea- water was 

 added, the sperm agglutinated. Table IV. shows the result of 



Table IV. 



Time of Transfer Per Cent. Per Cent, 



after Insemination Membranes. 2 Cell, 



in Normal Sea- Water. 



Immediate o o 



30 sec 80 20 



1 min 97 80 



2 " 97 92 



4 " 97 94 



8 " 97 97 



15 " 97 96 



30 " 97 97 



Inseminated control in sea-water 97 98 



Uninseminated controls. 



a. Sea-water o o 



b. AICI3 Eggs clumped. 



Viability test in 1 : 40,000 AICI3. June 19, 1922. 9 A. Eggs and sperm 

 fresh. Insemination 1 : 25 : 7.5. Exp. 1 : 00 P.M. Temp. 21.5 C. 



a viability test on eggs inseminated in normal sea-water and 

 later transferred to the membrane-inhibiting concentration of 

 the salt. It will be noticed by an examination of this table, 

 that the membrane-inhibiting concentration is more toxic to the 

 first cleavage than is the case with the other metallic salts. 



A test of the increase of membrane elevation due to an increase 

 of sperm concentration showed that the percentage was raised 

 from o per cent, to 32 per cent, on increasing the amount of 

 sperm from 1 drop to 15 drops of the 1 : 25 suspension in imme- 

 diate inseminations. 



6. Platinic Chloride. — In the case of no other metallic salt 

 studied is there as sharp a line of demarkation between concen- 

 trations which permit of membrane elevation and those which 

 are absolutely inhibitory, as with PtCl 4 . A stock solution was 



