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 



-G 



germ cells and that 

 these germ cells dif- 

 Eg g with^germ- fer from the somatic 



inal vesicle (A) and " Nucleolo " (AO. cells in the pOSSCS- 



B. Egg containing many cleavage nuclei. 4.1, 



C. Formation of primordial germ cells SlOn OI part OI the 

 (G) at posterior end of an egg. (From disintegrated " UU- 

 Sihestn, 1908.) 



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, 



