THE PHIDOGENETIC FLY, MIASTOR 63 
During the shortening and broadening of the germ 
band the group of eight oéjgonia of the third order 
becomes separated into two rows of four each — one 
row on either side of the body in the region of the 
eleventh segment (Fig. 22). Each group of four 
odgonia then becomes surrounded by a layer of 
mesoderm cells and forms a more or less spherical 
body which may now be called an ovary (Fig. 23). 
Soon after this occurs, the odgonia begin to divide 
again (Fig. 23, a) and by successive mitoses there 
are formed oégonia of the fourth, fifth (Fig. 24), and 
sixth orders. This completes the number of odgonia, 
which is typically thirty-two in each ovary, and 
provides us with the only case thus far on record 
where the number of odgonial divisions during the 
multiplication period in the history of the germ 
cells is known (Fig. 26). 
There are then six of these odgonial divisions 
between the formation of the single primordial germ 
cell and the production of the complete number of 
odgonia in the two ovaries. Some of the odgonia of 
the fifth order may be prevented from dividing, in 
which case of course there are less than thirty-two 
germ cells in each ovary. And not all of the odgonia 
in the ovary succeed in developing into odcytes and 
larvee, since a struggle for supremacy takes place 
among the germ cells resulting in the survival of only 
a few offspring, as may be determined by the fact, 
already referred to, that one larva gives rise as a 
rule to only from five to seventeen daughter larve. 
Each oégonium that succeeds in developing becomes 
