STUDIES ON GERM CELLS 529 
ensues during which the granular stage (fig. 73) is succeeded by a 
heavy network (fig. 74); this is followed by condensation into a 
solid mass (fig. 75), the formation of a heavy network again 
(fig. 80), the thinning out of this network (fig. 81), and finally 
the breaking up of the threads into many large irregular granules 
(fig. 82). 
3. Hymenopterous gall-flies 
There is still much to be learned regarding the life-cycles of the 
gall-flies, but what we do know is enough to prove that these 
insects offer a very profitable field for research. Examinations 
of the growing oocytes of certain Hymenopterous gall-flies 
have revealed many interesting structures that have a bearing 
upon the conditions described in the preceding part of this 
contribution and, although much more work needs to be done, 
the data already obtained are included here to indicate the wide- 
spread occurrence of phenomena described above. The oogene- 
sis in these insects is more difficult to study than in the parasitic 
Hymenoptera because fewer stages of growth are represented by 
the oocytes in a single individual. 
The maturation spindle in the oak-knot gall-fly, Andricus puncta- 
tus. The oak-knot gall-fly lays a pear-shaped egg (fig. 83), from 
the anterior end of which extends a long, slender process with an 
expanded terminal portion. This process resembles those de- 
seribed by Korschelt (’87) in Ranatra linearis. The two long 
slender processes extending from the anterior end of the eggs of 
Ranatra, arise from a single bud-like protuberance at one side 
of the anterior end of the oocyte, and their place of origin alter- 
nates from one side to the other in the row of oocytes which le 
in the lower part of the ovariole. When the eggs are laid, the 
processes are left extending freely out into the water from the 
decaying wood in which the rest of the egg is imbedded by the 
female. 
The egg of the oak-knot gall-fly shown in figure 83, was taken 
from an adult which was just about to emerge from the gall. 
At one side near the anterior end could be seen a spindle-shaped 
body—the nucleus of the egg. Several stages in the develop- 
