ZOOLOGY: HEGNER AND RUSSELL 
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in figure 4 preparing for division. One of these cells (nc) is smaller 
than the other and gives rise to nurse cells only. The other, the oocyte 
grandmother cell (ogmc) is larger and contains within its cytoplasm 
portions of a deeply staining body that we do not hesitate to homologize 
with the 'anello cromatico' of Giardina and which we may call the 
^oocyte determinant.' Between the two cells is an intercellular strand 
(is) which represents the remains of the spindle fibres of the previous 
mitotic division. 
A four-cell stage such as is illustrated in figure 5 proves that the 
division of the oocyte grandmother cell (fig. 4, ogmc) is differential 
since one cell, the oocyte mother cell (fig. 5, omc) has received all of the 
uo 
6. Diagrammatic representation of oocyte differentiation in Dineutes nigrior. uo = 
ultimate oogonium, containing oocyte determinant within its nucleus; ogmc = oocyte grand- 
mother cell having similar nuclear characteristics; omc = oocyte mother cell, o — oocyte. 
Plain circles indicate nurse cells. 
oocyte determinant (od), whereas the other three (nc) are smaller and 
lack this body, and are destined to become nurse cells. The intercellu- 
lar strands are quite conspicuous here and leave no doubt in the mind of 
the observer as to the origin of the four cells from a single cell, the ulti- 
mate oogonium. Each of these four cells undergoes a single mitotic 
division resulting in the formation of seven nurse cells and one oocyte, 
the latter containing the oocyte determinant. 
The most conspicuous difference that we have discovered between the 
