498 ROBERT W. HEGNER 
and those in a single rosette have descended from a single mother 
cell which may be called the oogonial mother cell. The actual 
differentiation of the oocytes and nurse cells occurs in a much 
shorter part of the ovariole (d). After the oocytes are definitely 
established, they move down the ovariole, become arranged in a 
single row (0) and are gradually separated from each other by 
groups of nurse cells (n) which le in nurse chambers just above 
them. The elements within ovarioles of different ages differ, 
of course, both in their stage of development ‘and in their 
distribution. 
The three kinds of cells within the ovaries of insects are the 
oocytes, nurse cells, and epithelial cells. These three kinds 
of cells arise differently in different groups of insects. Thus 
the nurse cells and epithelial cells in the paedogenetic fly, Miastor 
(Kahle ’08; Hegner 714 a) are of mesodermal origin and the germ 
cells give rise only to oocytes. In the Hymenopteraon the 
other hand Korschelt (’86) in Bombus, Paulcke (’01) in Apis, 
and Marshall (’07) in Polistes agree that the three cellular ele- 
ments within the ovaries arise from one sort of cells, the germ 
cells. I have been unable to determine the origin of the epithe- 
lial cells in the ovarioles of the bee because of the lack of young 
ovaries, but that nurse cells and oocytes arise from oogonia 
there can be no doubt. 
Part of the rosette region of an ovariole is shown in figure 2. 
Two kinds of cells are present, (1) Those that make up the 
rosettes (r); and (2) the epithelial cells (e) among the rosettes. 
The ground substance within the ovariole in this region appears 
to be a loose cytoplasmic reticulum containing a few scattered 
nuclei. These nuclei are rather irregular in shape, and contain 
a clear matrix in which may be seen one or two large chromatin 
masses and a very delicate reticulum. No epithelial cell bound- 
aries could be observed in this part of the ovariole and it seems 
probable that the rosettes are imbedded in a syncytium. There 
seems to be no regular arrangement of the rosettes; they do not 
crowd one another, but the cells in each are closely united, hence 
it is a very simple matter to distinguish the separate rosettes 
in an ovariole even with low magnification. It seems strange 
