No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 441 
next the cell membrane gradually disappears; then the chro¬ 
matin granules no longer become colored by any of the stains 
employed, but become refractive and yellowish. All the chro¬ 
matin granules do not lose their affinity for stains simulta¬ 
neously, but two or three of them may often remain stained as 
before, while the remaining granules of the same nucleus may 
have entirely lost their stain. At this period in the nuclear 
degeneration we find small masses of these unstaining, yellow¬ 
ish granules in the cytoplasm, each mass still preserving the 
form of a nucleus. Later these individual granules wander 
apart, or those of several nuclei may partially fuse together to 
produce a larger mass ; these larger masses of granules are 
always enveloped by a clear zone of cytoplasm, sometimes of 
considerable extent, so that they appear to be situated in 
vacuoles of the cytoplasm. The degeneration stages of these 
nuclei are most frequent in the cytoplasm, before yolk balls 
begin to arise in it ; as the latter appear, the remnants of the 
degenerated nuclei gradually vanish, so that when the cell is 
filled with the yolk balls all vestiges of these nuclei have 
vanished. We must suppose that they become assimilated by, 
or dissolved in, the cytoplasm. These formations, the katabolic 
changes of degenerating nuclei, can in no way be confounded 
with stages of yolk development, since the small size, yellowish 
color, and refrangibility of these granular masses serve to dis- 
- tinguish them sharply from any stage of the yolk balls, even 
though both are often found in the immediate vicinity of each 
other. 
The nuclei which are destined to become germinal vesicles 
increase in size to some extent before nucleoli appear in them; 
they now differ from the connective-tissue nuclei, apart from 
their greater dimensions, in having a relatively greater amount 
of chromatin and in being regularly spherical or oval in form. 
The first nucleoli to arise always lie in close contact with the 
inner surface of the nuclear membrane (Figs. 214, 216, 219, 
220, 224, 225). They usually appear in the form of a thin 
disc-shaped mass on the inner surface of the membrane, but 
there is considerable irregularity in the form of this mass, which 
may be angular or nearly spherical in outline. At the com- 
