STUDIES OF FERTILIZATION. 14! 



Mercury thus exhibits an extraordinary contrast to copper: 

 in certain comparable concentrations it paralyzes sperm, copper 

 does not; it produces membrane formation alone, and favors 

 it in fertilization, copper inhibits membrane formation; it sup- 

 presses cleavage and cytolyzes fertilized eggs rapidly; copper 

 is neutral during the same stages. 



The differences in the actions of copper and mercury respec- 

 tively on fertilization may be explained by differences in intensity 

 of action on the early and the later stages of fertilization respec- 

 tively. In the case of mercuric chloride I have found that the 

 inhibiting action in fertilization (which occurs at higher concen- 

 trations than in the case of copper, as for instance in solutions 

 5 and 6 of Table VII.) is reversible, like copper. Specifically, 

 eggs that remain unfertilized in these solutions may be fertilized 

 after return to sea-water, if the exposure is not too long (about 

 20 minutes). Presumably, therefore, mercury acts like copper 

 in the initial stages of fertilization, though a higher concentration 

 is required; but in the later stages mercury acts deleteriously 

 in much lower concentrations than copper; one part of HgCl 2 

 in 625,000 parts of sea- water will completely inhibit cleavage 

 of fertilized eggs, whereas it requires about one part of CuCl 2 

 in 62,500 parts of sea- water to produce comparable effects. 



The comparison may be tabulated as follows according to the 

 stages of fertilization : 



1. Agglutination of the spermatozoon to the egg. 



2. Latent period. 



Copper intervenes, Hg not, or Cu>Hg. 



3. Combination of sperm receptors with fertilizin. 



4. Activation = combination of fertilizin with egg receptors. 



5. Sterilization = "wave of negativity." 



6. Spermatozoon enters the egg. 



7. Membrane formation. 



8. Hg>Cu in later events. 



It is well known that the salts of heavy metals have a powerful 

 "poisonous" effect on enzymes. McGuigan (1904) determined 

 that for diastase the order of poisonous effects (complete inhibi- 



