DEVELOPMENT OF PARACOPIDOSOMOPSIS 9 



sexual larvae. Hegner ('14) has elaborated this idea, and classi- 

 fies the nucleolus as a germ-line determinant, I have elsewhere 

 ('17 a) pointed out the difficulties which stand in the way of 

 accepting this interpretation, especially as regards its applica- 

 tion to the origin of the asexual larvae in Litomastix and Paracopi- 

 dosomopsis. 



I have gone into the subject of the origin and function of the 

 nucleolus rather fully with the hope of showing how necessary 

 it is that a reinvestigation of its genesis and fate should be made. 

 Perhaps this could best be done by the methods employed in the 

 study of mitochondria. 



h. Maturation 



1 have elewhere ('18) described maturation and fertilization, 

 and the account given here may be confined to a brief statement 

 of the principal points of interest. 



1 . The first maturation. The process of maturation is identi- 

 cal in fertilized and unfertilized eggs. As is the case in many 

 other hymenoptera, the maturation divisions involve only the 

 chromatin, and consequently distinct polar bodies are not formed. 

 The first maturation spindle is formed about fifteen minutes 

 after the egg is laid, and within the next ten or fifteen minutes 

 the chromosomes have reached the late anaphase stage (fig. 3). 

 The long axis of the spindle is not quite parallel with that of the 

 egg, but it meets the latter at a slightly oblique angle. This 

 brings the outer end of the spindle near to the surface of the egg 

 at the base of the anterior process. The chromatin of the first 

 polar body is therefore found in this region. 



The first maturation division results in reducing the number of 

 chromosomes from sixteen to eight (figs. 26 to 28). In certain 

 cases one can easily count eight chromosomes in the first polar 

 body and in the second oocyte (e.g., fig. 27). 



2. The second maturation. The second maturation follows 

 almost immediately after the first is completed, without the 

 reorganization of a nucleus. Likewise the first polar body chro- 

 matin forms a spindle and divides without forming a nucleus. 

 These two divisions may occur simultaneously (fig. 29), or the 



