PLASMA-STRUCTURE IN EGG OF HYDRACTINIA 197 



at this stage no basic-staining granules that correspond to Schaxel's 

 intra-vitelHne chromatin'* (fig. 14). 



No one staining method differentiates these various types of 

 structure, since, as a rule, all stain the same way with certain 

 dyes used after some killing fluids. For example, as shown in 

 table 1, if iron-hematoxylin is used on material in Flemming's or 

 Meves' kiUing fluids, all the elements take the hematoxylin 

 stain in slightly varying degrees of intensity (fig. 16). By the use 

 of various killing fluids and stains, however, they can be shown 

 to be distinct elements in the following way (table 1). 



The oily bodies are most easily distinguished from the yolk 

 since the former darken somewhat in osmic acid. After staining 

 in saffranin and methyl-violet they take a deep violet color, while 

 the yolk is red. Also, the oil can be completely separated from 

 the other cell-elements by centrifuging the egg. 



The two kinds of yolk, simple and compound (often indistin- 

 guishable from each other when iron-hematoxylin is used after 

 Meves' or Flemming's fixation) show their individuality when 

 stained either with Benda's stain or with saffranin and methyl- 

 violet. These stains reveal, in certain of the spheres, drops or 

 globules which stain differently from the ground-substance of 

 the sphere. The geometrical regularity of these is shown in 

 figure 15, in which young and old compound spheres are repre- 

 sented. After the use of Benda's stain the mature simple yolk 

 is uniformly violet in color, while the compound spheres show 

 brilliant violet globules in a yellow ground-substance. When 

 stained in saffranin and methyl- violet, the globules of the compound 

 sphere are brilliant red and the ground-substance light lavender, 

 while the simple yolk is reddish violet. The most striking differ- 

 entiation appears in material fixed in picro-acetic killing fluid 

 and stained in iron-hematoxylin and light green, for the simple 



^ These elements are diagrammatically represented in figure 14 in the following 

 manner: Young yolk is represented by solid gray circles; mature simple yolk is 

 represented by hollow circles; mature compound yolk is represented by hollow 

 circles containing small circles; oil is represented by hollow circles containing 

 dots; mitochondria are represented as black rods; the protoplasm is uniformly 

 gray. 



