COPPER, ENZYMES, AND FERTILIZATION. 87 



tion by a marked yellow brought about by potassium ethyl xanthate. 

 Again the triple-nitrite test was positive. Under the microscope 

 the treated membranes showed numerous irregular blotches and 

 specks of black. By prolonging this treatment for thirty minutes 

 and following it with a short exposure to ioo° C, the membranes 

 became closely speckled with black and underwent a discoloration 

 quantitatively more in harmony with the very marked reaction 

 gotten with ammonia and potassium ethyl xanthate. The copper 

 in this membrane is, therefore, also " masked " ; moreover, the dis- 

 covery of copper in the Arbacia egg membrane does not stand 

 alone. 



3. Copper in the Chorion. 



Since the pigment during its outward passage permeates the 

 chorion, the latter necessarily contains traces of copper. There is 

 also some direct evidence of this, for haematoxylin imparts to the 

 jelly a light bluish tint, whereas the triple-nitrite test brings out a 

 few scattered granules stained black. Infinitesimal quantities of 

 copper, then, can be demonstrated directly in the chorion. 



4. Copper and the Cortex. 



Inasmuch as Lillie (loc. cit.) has assumed the presence of a 

 copper-avid substance in the cortex of the egg, I paid especial 

 attention to this region both in untreated sections and in those 

 exposed to reagents for copper. 



Unquestionably the cortex differs from the remainder of the 

 egg. Yolk, pigment, and other visible granules are absent. The 

 zone immediately beneath the egg membrane, even at very high 

 magnifications, seems to be optically clear. In sections not ex- 

 posed to reagents for copper the cortical layer appears blue — no 

 doubt the result chiefly of refraction. Nevertheless the color is 

 intensified by ammonia and haematoxylin and does not disappear 

 entirely when viewed by light transmitted through ground glass 

 nor after the sections have been cleared in glycerine, xylol, or 

 balsam. 2 



Furthermore, perhaps on account of distortions through shrink- 

 age, the blue layer, instead of being in immediate contact with the 



2 There are, of course, other effects of refraction throughout the egg. 



