174 Schrader. 
the anterior pole (Fig. 21) or it may follow the periphery of the ege. 
In either case, the giant cells encounter the symbionts. What the 
occasion for this movement is, I am not prepared to say. In a few 
eggs, the blastoderm cells in the immediate vieinity of the symbionts 
are elongated in the direetion of the symbiotie mass, as though the 
latter exerted some attraction upon them. This does not suffice in the 
case of blastoderm cells to separate them from the periphery (Fig. 22), 
and at best, such attraction if existing, is only temporary. The giant 
cells, however, push in between the symbiont spheres and surround 
them, forming a compact cellular mass. This new association is the 
result of a gradual and rather slow process. Due to this fact, the 
steps in the formation of this compound cell mass can be followed one 
by one. Thus during the primary stages only a few giant cells are 
entering in between the scattered symbionts, the major number still 
forming a more or less definite group at one side (Fig. 22 und 29). 
Gradually, more and more of the cells enter into association with the 
symbionts (Fig. 23), until in the final stages only a few or none at 
all are free on the outside (Fig. 24 and 37). Only in the earlier phases 
of this process is division still seen in the giant cells. In later stages, 
mitotic figures are very rare, but the nucleoli, size, and general struc- 
ture of the cells are as characteristie as before. 
As intimated, some time elapses in the establishment of this 
association. The giant cells become separated from the periphery as 
the germ band first begins its growth. This growth takes its origin 
from a point close to the posterior pole, and is accompanied by a 
general thinning of the blastoderm cells around the rest of the egg. 
The latter proceeds until the cellular nature of this envelope of the 
egg can be made out only with difficulty (Fig. 27 to 32). Very often, 
there is a migration of some of the yolk cells to the periphery before 
the giant cells have reached the symbionts, and at times some yolk 
cells may become temporarily associated with the symbionts. This 
association is, however, only an accidental and temporary one, and soon 
these cells find their way to the periphery, so that before the giant 
cells reach the symbionts in their turn, the latter are once more free 
from any cellular entanglement. 
Pseudococeus thus is one of the seemingly rare cases in which 
normal polar bodies do not disintegrate soon after formation. Analogous 
cases are few in number. Neglecting the case of the polyclad Prosthe- 
ceraeus (FRANCOTTE, 1898), they are found only in the Hymenoptera. 
