274 



LEIGH HOADLEY. 



In this series, a sperm suspension was made by adding a number 

 of drops of the dry sperm to 7.5 c.c. of the membrane-inhibitory 

 concentration of the metallic salt, and the effect of the solution 

 on the behavior of the sperm was noted. A drop of NaOH 

 (iV/500) was then added to one preparation and its effect noted. 

 To another preparation, a drop of concentrated egg sea-water 

 was added. The results may be seen in Tab'e VIIc. 



c. Summary. 



In summarizing the results of the foregoing experiments, it 

 may be generally stated, that, with the exception of HgCl 2 , all 

 of the metals studied have three effects on the fertilization 

 period of Arbacia. The first and second occur at a greater 

 dilution than the third and involve membrane elevation. When 

 eggs are inseminated directly in certain solutions, they give no 

 cortical response, i.e., the effect is immediate and prevents any 

 reaction between the gametes themselves; if, however, eggs are 

 placed in this same solution after cortical discharge has begun 

 but before it is complete, a "narrow membrane" results which 

 may be attributed to an incomplete cortical response. The 

 third involves the subsequent events and requires a higher 

 concentration of the metallic salt. It seems from the data to be 

 cumulative in its action. When the eggs are placed in the 

 solutions five minutes after the insemination in normal sea-water, 

 the time factor amounts to approximately forty minutes, as first 

 cleavage is used as an indicator. If the eggs are transferred at 

 a later time, first cleavage may be only partially inhibited but 

 there will be no second cleavage. That is to say, the time re- 

 quired for the salt solution to produce its toxic effect is, in these 

 experiments, about thirty-five or forty minutes. Table VIII 

 gives a comparison of the concentrations necessary to produce 

 these effects. The order of toxicity of the metallic salts will be 

 seen to be the same for both membrane effects as well as subse- 

 quent events. The general results are in accord with those 

 noted by Lillie in his work on copper. Mercury, as has been 

 observed above, is an exception to this general rule. 



In each case, as can be seen by reexamination of Table VIIc, 

 sperm may be caused to agglutinate in the membrane-inhibitory 



