STUDIES OF FERTILIZATION. 139 



inhibitors work in the egg. No other hypothesis possesses the 

 simplicity of this one, which means that the activating substance 

 of the egg (fertilizin) is present in the egg-water. 



9. The Effect oj Copper on Activation by Butyric Acid. 



If copper chloride inhibits fertilization by combining with the 

 fertilizin of the egg it should also inhibit activation of the egg by 

 parthenogenetic agents as, e.g., butyric acid. This consequence 

 of the theory was found to be true. If unfertilized eggs of 

 Arbacia are placed in 50 c.c. sea-water + 2 c.c. N/io butyric 

 acid, and transfers are made to 1/500,000 copper sea-water and 

 to sea- water for control, after 30 seconds and 45 seconds, it is 

 found that in the sea-water good to fair membranes form on 

 practically all of the eggs in about two minutes; but in the 

 1/500,000 copper sea-water no membranes form and the eggs 

 appear entirely unchanged for at least twenty minutes. Then 

 a gradual cytolysis begins to set in, entirely similar to the cy- 

 tolysis that occurs in copper sea-water without previous exposure 

 to butyric acid after two to three hours. The butyric acid has 

 hastened the appearance of the copper cytolysis; but the copper 

 has entirely inhibited the typical membrane-forming reaction. 



Copper present with the butyric acid does not, however, 

 inhibit the membrane formation after transfer to sea-water. 

 In this reciprocal experiment one part of copper chloride is 

 added to 500,000 parts of the butyric acid solution, and the eggs 

 receive the normal exposure. When transferred to sea-water, 

 membranes form just as though the copper had not been present. 

 Thus, whatever the pre-activation effect of the butyric acid 

 may be, copper does not inhibit it, but operates only to prevent 

 the activation of the fertilizin. 



Similarly in fertilization the preliminary effect of the sperma- 

 tozoon in preparing the fertilizin for discharge ("latent period"; 

 see p. 141) is not presumed to be affected by the copper but only 

 the actual discharge (i.e., activation) of the fertilizin. 



10. A Comparison of the Effects of Mercuric Chloride. 



It will be desirable to compare the effects of the salts of other 

 heavy metals on fertilization, and some experiments have been 

 begun along this line. However, in this paper, mercury alone 

 will be considered. 



