BIOLOGY OF PARACOPIDOSOMOPSIS. 59 



have demonstrated that it arises outside the germinal vesicle, 

 and therefore does not represent a true nucleolus. Silvestri 

 ('14) has later admitted the correctness of their conclusions, 

 and proposed the term "oosoma." As to the fate of this body, 

 Silvestri showed that it enters into certain definite cleavage cells, 

 which he believed give rise to germ cells. Hegner has elaborated 

 this idea, bringing it into harmony with his well-known views on 

 germ-line-determinants. 



The sperm is invariably found in the posterior half of the egg 

 (Figs, i, 2, 8), indicating that insemination must take place 

 at any point on the surface of the broad end of the egg. The 

 entire sperm enters the egg (Fig. 8), and soon thereafter forms 

 a small male pronucleus (Figs. I, 2, 13). There is no evidence 

 that polyspermy ever occurs in the egg of this species, as no egg 

 has ever been found with more than a single sperm in it. 



FIRST MATURATION. 



As in the eggs of many other Hymenoptera, the maturation 

 divisions of Paracopidosomopsis do not result in the formation 

 of distinct polar bodies, but instead only the chromatin under- 

 goes division. Preparation for the first maturation division is 

 seen in the appearance of heterotypic or bivalent chromosomes 

 in the early prophase stage. These are sometimes in the form 

 of V's and crosses, and in the clearest cases eight are present 



(Fig. 7). 



The position of the first maturation spindle is very constant. 

 It lies well toward the anterior end of the cell, with its long axis 

 directed toward the center of the egg (Fig. 8). In the anaphase 

 stage there is present a distinct mid-body at the equator of the 

 interzonal or spindle fibers (Figs. 8, 9). At the close of the 

 division the two groups of chromosomes are not reorganized 

 into nuclei ; but lie close together surrounded by clear spaces in 

 the cytoplasm. 



In only a few cases have I been able to determine accurately 

 the number of chromosomes that pass to either end of the first 

 maturation spindle. In Fig. 9 the outer, or first polar body group 

 contains eight chromosomes, and at the lower end at least seven 

 can be counted. In Fig. 10 the lower or second oocyte group 



