266 LEIGH HOADLEY. 



made from the crystals which was .9 per cent, in strength and 

 all the concentrations were made up by adding this to sea-water. 

 The test for the membrane-inhibitory concentration shows that 

 at 1 : 16,666, there is membrane elevation to equal the control, 

 while at 1 : 11, ill, there is a complete inhibition of membrane 

 elevation. The p.H. of the latter concentration is 7.4. In this 

 case each egg may be surrounded by from twelve to sixteen very 

 active sperm. They strike the membrane and remain agglu- 

 tinated to it though they are unable to incite any cortical change 

 whatever. The agglutination of the sperm, by a drop of egg 

 sea-water, in such a PtCl 4 solution when the suspension is made 

 up directly in the solution, is good. The inhibition comes after 

 the agglutination and before the cortical response of the egg can 

 show itself, i.e., it occurs in the latent period. 



Not only is there a sharp distinction between concentrations 

 which allow complete membrane elevation and those which are 

 absolutely inhibitory, in the case of this metal, but the membrane- 

 inhibiting concentration and the cleavage-toxic concentration 

 are both more rapidly toxic to the eggs than is the case with the 

 other metals studied. Table Va shows the results of a viability 



Table Va. 



Time of Transfer 

 after Insemination in Per Cent. Per Cent. 



Normal Sea-water. Membranes. ist Cleavage 



Immediate o 



30 sec 88 44 



92 SO 



96 62 



15 

 30 



84 

 84 

 98 

 97 



Inseminated control in sea-water 98 98 



Uninseminated control in sea-water o o 



Viability test in 1 : 11,111 PtCLi. June 30, 1922. Eggs 9 : 00 A.M. 9 A. 

 Sperm fresh. Insemination 1 : 25 : 7.5. Experiment 10 : 00 A.M. Temp. 21° C. 



test at the membrane-inhibiting concentration of this salt; 

 Table Vb shows the effect of such a solution on eggs which have 

 been forced to produce membranes by the use of an excess of 

 sperm; Table Vc shows the result of a viability test at the 

 cleavage-toxic concentration. All of these tests show the great 

 poisonous effect of the solution on the egg. The test with the 



