PLASMA-STRUCTURE IN EGG OF HYDRACTINIA 203 



brown). In my material, as shown in the figures, there are no 

 nests of 'extra-nuclear' granules within which yolk-material 

 with a different staining reaction is secreted, as described by 

 Schaxel. There is, rather, a graded series from the smallest 

 spherical granules to the largest spheres; and these latter do not as 

 yet differ in staining reaction from the pseudochromatin-granules, 

 a condition subsequently seen. 



A little before the egg is half grown, however, a change of 

 staining reaction begins. A few of the largest yolk-spheres change 

 their reaction in the Benda stain, the brown of the alizarin being 

 replaced by violet. Figure 19 shows such an egg under low magni- 

 fication, while figure 12 represents this change diagrammatically. 

 As the egg grows, more and more of the yolk-spheres take the 

 violet color until the whole egg is dominated by violet, a few small 

 yellow ones remaining among the large violet spheres (figs. 13, 14, 

 diagrammatic) . This change in staining reaction is very striking 

 on a slide in which all stages in the growth of the egg are present, 

 when obviously they have all received the same treatment in the 

 staining process. 



These points are less strikingly but well shown when some of the 

 same material is stained in iron-hematoxyhn, since the pseudo- 

 chromatin-granules are grayish, the young yolk gray, the nature 

 yolk black (figs. 16). Although picro-actic and sublimate-acetic 

 fixations are poor for determining the development of the yolk, 

 the change in staining reaction is even more strikingly shown 

 when iron-hematoxylin counterstained with light green is used, 

 since the granules of the young egg take an intense black, while 

 the yolk-spheres of the mature egg are green. This fixation 

 also makes it evident that the pseudochromatin-granules as such 

 are not present in the mature egg between the yolk-spheres ('intra- 

 vitelline chromatin' of Schaxel) for there are no deeply staining 

 granules present in such eggs, while young eggs after the same 

 treatment are dominated by black granules. 



b. Development of the compound yolk. Since the young stages 

 of the simple yolk-spheres and the compound spheres stain alike, 

 they cannot be distinguished from one another until they are 

 nearly grown, when internal globules appear in the compound 



