GERM CELLS IN THE ARTHROPODA 149 



posterior " massa monembrionale, " which produces 

 the so-called asexual larvae. These lack reproductive, 

 respiratory, circulatory, and excretory systems. They 

 are supposed to develop from cell masses which do 

 not contain descendants of the cell with " nucleolar" 

 material, and to serve the purpose of tearing apart 

 the organs of the host, thus making it available as 

 food for the normal larvae. The " massa monem- 

 brionale," according to this view, consists entirely of 

 somatic cells, whereas the "massa germinigera" 

 possesses both somatic and germ cells. Doubts 

 have been expressed regarding the development of 

 the asexual larvae, and Silvestri's results need con- 

 firmation. There seems to be no doubt that the 

 "nucleolo" is a keimbahn-determinant in both 

 monembryonic and polyembryonic HYMENOPTERA, 

 but its identification as the nucleolus from the oocyte 

 nucleus did not seem to the writer to be well estab- 

 lished. Its history was, therefore, studied by the 

 writer (Hegner, 19146) during the growth period of 

 the eggs, with the following results. 



My material consisted of a brood of females 

 belonging to the polyembryonic species Copidosoma 

 gelechicB. As in most other insects, the two ovaries of 

 Copidosoma consist of rows of oocytes in various 

 stages of growth the oldest and largest near the 

 posterior end, and the youngest and smallest at the 

 opposite pole. Before the oogonia enter the growth 

 period (Fig. 46, A, o) each becomes surrounded by 

 a follicular epithelium (fe) and is provided with a 

 group of nurse cells (nc) which likewise are enclosed 



