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 oocytes, the nucleus is central, but 

 during growth it moves to the periphery, as shown by Smallwood ('99) 

 and Hargitt (:00, :04'=). 



The germinative vesicle in the growing egg show^s 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. The 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 oogenesis, 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, mean^ 

 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 



