86 OTTO GLASER. 



the cytologists, black. If the material is kept moderately warm 

 on a water bath and the reaction is permitted to continue for half 

 an hour, the pigment bodies themselves become distinctly bluish or 

 even black. This suggests a gradual unmasking of the copper in 

 Macallum's sense ('12). 



2. Copper in the Egg Membrane. 



A definite visible membrane ('13 1 ) invests the unfertilized 

 Arbacia egg and constitutes a barrier through which pigment must 

 pass in order to reach the outside. If now the pigment itself con- 

 tains copper, the same thing might easily be true of the membrane 

 through which it passes. 



But the membrane is by nature yellowish-brown. This excludes 

 tests depending on the formation of cupric cyanide, ferrocyanide, 

 or xanthate. With hematoxylin a bluish tint develops, and this 

 could be interpreted as evidence of copper if iron were absent. 

 However, since the latter is almost certainly present, we must fall 

 back on the triple-nitrite reaction. 



In this the original native yellow-brown of the membrane is 

 replaced with black. Under low powers the membranes are in 

 very sharp relief. The oil immersion, however, resolves their 

 uniform black, in optical section, into a series of irregularly spaced 

 discontinuous beads connected by an exceedingly thin continuous 

 black line. 



This test was repeated on several sets of sections. The results 

 were uniform and without inconsistencies. The evidence, then, 

 that copper exists in the Arbacia egg membrane appears valid ; yet 

 the quantities involved are so small that I felt impelled to check 

 the results on the hen's egg, whose vitelline membrane, I reasoned, 

 should contain copper if the analysis of the yolk by Fleurent and 

 Levi (loc. cit.) is correct. 



This supposition was readily substantiated by four different 

 methods. 



The vitelline membranes were removed from the yolk and 

 washed in a stream of running tap-water for twelve hours. In 

 this way all but negligible quantities of yolk were removed. 



After incineration a solution of the ash, upon the addition of 

 ammonia, turned blue. This test was supported in neutral solu- 



