CERTAIN EFFECTS OF THE SALTS OF THE HEAVY METALS ON THE FERTILIZATION REACTION IN ARBACIA PUNCTULATA

¹ THE HULL ZOÖLOGICAL LABORATORY, UNIVERSITY OF CHICAGO

In summarizing the results of the foregoing experiments, it may be generally stated, that, with the exception of HgCl₂, 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 required 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 subsequent 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 reëxamination of Table VIIc, sperm may be caused to agglutinate in the membrane-inhibitory concentrations by the addition of egg sea-water, thus demonstrating that the action is not primarily on the sperm before their interaction with the female gametes.