No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 463 
appear not to stain at all, and of a few delicate fibers, which 
stain a lilac color (Figs. 267-269). As the germinal vesicle 
increases in size these chromatin fibers gradually become 
thicker and more numerous, commence to stain more deeply 
with haematoxylin, and gradually connect together to build 
a chromatin reticulum ; the minute, unstained microsomes 
still occur between these fibers. Finally, in the largest nuclei 
at my command, and ones which had been fixed with the fluid of 
Flemming and stained by the triple stain of this cytologist, we 
find, in addition to the abundant unstained microsomes, short, 
rod-like masses of chromatin, which stain deeply with gentian 
violet, and each appears to be formed of a row of granules or 
thickened discs (Fig. 280). Whether the minute microsomes 
are true chromatin or are lanthanin (oedematin) granules is 
open to question ; the latter assumption might be the correct 
one. We notice two remarkable phenomena in the chromatin 
changes just depicted : (1) the grouping of the chromatin in 
the center of the nucleus, around the nucleolus, at the comple¬ 
tion of the mitotic stages ; and (2) immediately subsequent to 
the preceding, the lilac stain of the chromatin after haematoxy¬ 
lin. Now, concomitant with the former of these two phenomena, 
the yolk makes its first appearance in the cytoplasm, and as we 
have shown above, usually in the close vicinity of the nucleus. 
It would be quite erroneous to conclude that the yolk globules 
are in any way produced by the chromatin, as e.g. y by a migra¬ 
tion of chromatin particles out of the nucleus ; for in this stage 
all the chromatin is removed from the periphery of the nucleus. 
On the other hand, however, I would suggest the hypothesis 
that the reason for the chromatin being removed from the 
periphery of the nucleus is because at this period the peripheral 
portion of the latter is chiefly concerned in the assimilation of 
yolk substance from the cytoplasm. In support of this assump¬ 
tion the fact may be recalled that in the following stage the 
chromatin fibers are stained a lilac color, as if they were stained 
with eosin, as well as haematoxylin, and not as before, simply 
with the former stain ; this would show that during this period 
there is an addition of a cytoplasmic substance to the chromatin 
fibers, perhaps allied to the substance of the yolk globules, and 
