146 GERM-CELL CYCLE IN ANIMALS 
of divisions a number of nuclei which migrate to 
the periphery, as is the rule in insect development. 
The “ nucleolo” remains during this cleavage period 
unchanged near the posterior end (Fig. 44, B); then, 
when cell walls appear, it becomes distributed among 
several of the cells 
thus formed. These 
multiply less rapidly 
than the other em- 
bryonic cells and are 
the only cells that 
give rise to the germ 
cells in the adult. 
It is thus obvious 
that there is here an 
early segregation of 
germ cells and that 
these germ cells dif- 
Fic. 44.—Oéphthora. A. Egg with germ- fer from the somatic 
inal vesicle (A) and ‘“Nucleolo” (N). eells in the posses- 
B. Egg containing many cleavage nuclei. . 
C. Formation of primordial germ cells sion of part of the 
Ca eg end of an egg. (From disintegrated “nue 
cleolo.” 
The polyembryonic species described by Silvestri 
are Copidosoma (Litomastix) truncatellus and Agenias- 
pis (Encyrtus) fuscicollis. The eggs of these species 
when laid are vase-shaped (Fig. 45), the posterior 
end corresponding to the base of the vase. Here 
also a germinal vesicle and ‘‘ nucleolo”’ are present, 
the latter almost always near the posterior end. 
Parthenogenetic eggs were found to produce males, 
