COPPER, ENZYMES, AND FERTILIZATION. 93 



These changes become intelligible if we assume, in the one case, 

 the formation of minute traces of copper xanthate ; in the second, 

 of copper ferrocyanide. Since the same reagents produce no 

 noticeable changes in these locations in untreated material, it 

 appears that the cortex of an egg exposed to copper contains more 

 than the normal quantity of the metal. Moreover, the excess is 

 localized chiefly near the surface, and since it is not the agglutinin 

 that is copper bearing, but the lipolysin, it appears probable that 

 the latter is also concentrated immediately under the vitelline 

 membrane. 



X. Copper Map of the Normal Egg. 



From all these tests — those on the controls as well as those on 

 material exposed to copper sulphate, I have constructed a chart 

 which indicates the distribution of copper in the normal Arbacia 

 egg. This map is a visual summary of the chief results and infer- 

 ences, and in view of the preceding discussion seems to require no 

 other comment than that given in the legend under the figure. 



Diagram showing distribution of copper in the normal egg of Arbacia 

 punctulata. The central clear area is the nucleus. Immediately about this, 

 and extending to the cortex, the larger black spots represent pigment granules 

 in which copper was demonstrated indirectly by analysis of secreted pigment 

 and directly, in situ, as potassium-copper-lead nitrite. The latter, as well 



