HARGITT: PENNARIA TIARELLA AND TUBULARIA CROCEA. 165 
network, which is, connected to the nucleolus. by fine strands. ‘The 
nucleolus itself seems to be composed entirely of non-chromatic matter, 
for.in Conklin’s picro-hematoxylin mixture it stains yellowish, while 
the chromatin is bluish; in hematoxylin and eosin the nucleolus is red, 
the nuclear reticulum blue or purple. In the nucleolus at this stage, 
there are present one or more vacuoles, which may disappear during 
the growth period. In.a few instances the nucleolus has taken some 
of the chromatin stain, appearing. brownish in picro-hematoxylin, or 
slightly purplish in hematoxylin,,and eosin. . It, may therefore some- 
times contain a little chromatin, though apparently this is not usually 
the case, provided, the staining reactions are to be regarded as at all 
specific. In early stages of the: odcytes,: the nucleus. is central, but 
during growth it- moves to the apa a as shown by Smallwood (’99) 
and Hargitt (:00, :04°). 
The germinative vesicle in the growing egg ne a very. faintly 
stainable reticulum, and the chromatin is. apparently finely divided 
and diffused along the network. This condition, as is: well known, 
exists. in many Hydromedusae and in some other animals. ‘Ihe nu- 
cleolus at this stage is nearly spherical, usually excentric, often markedly 
so (Figs. 1-4), and may contain vacuoles, though, more commonly it 
appears homogeneous. ‘The nucleolus selects the plasma.stain at this 
stage also. At.the end of the growth. period, the nuclear reticulum 
shows so little affinity for basic stains that there appears to be, so far 
as this test shows, no chromatin present in the entire nucleus. . I can 
suggest no explanation for this peculiar condition of the chromatin 
at this period, but it is normal and characteristic of this stage. 
The staining reactions of the nucleolus above described make it 
probable that this body is,composed mostly, if not entirely, of non- 
chromatic matter. Since I have not. studied the very early stages in 
the odgenesis, and do not know how the nucleolus originates, it is not 
possible to say that there is no direct relation between the nucleolus 
and the chromosomes. ‘The fact that the nucleolus does not change 
its staining, reaction during the growth period.of the egg, while the 
chromatin. becomes diffused and loses its staining capacity, means 
either that the chromatin does not enter the nucleolus, or, at least, 
that it does not enter as chromatin.. ‘The further fact that the nucleolus 
does not. enlarge during the growth of the egg, makes it nearly certain 
that the chromatin does not then enter it. It is likewise true that the 
concentration of the chromatin of the germinative vesicle into granules 
and strands just before polar cells are formed, is. not necessarily coin- 
cident with the disappearance of the nucleolus (Figs. 1,3). In some 
