43 ELMER L. SHAFFER. 



of germ-cell origin" (Hegner, '14, page 119). In Dytiscns, 

 Giardina ('01) has shown that germ-cells and nurse-cells arise by 

 differential divisions of a stem-cell. In Cicada, I am unable to 

 ascertain the origin of the cell-elements of the ovary from a 

 study of the pupal and adult ovaries. The differentiation of the 

 cells must take place at a comparatively early time in the long 

 life cycle of the insect. 



There are two ovaries, each consisting of a great many ovarian 

 tubules, the ovaries of the adult being much larger than those 

 of the pupae, due to the presence of a large number of mature 

 eggs. Figure 34 is that of a longitudinal section through an 

 ovarian tubule of an adult recently emerged from the pupal 

 case and it will at once be seen that it is a typical Hemipteran 

 ovarian tubule. At the proximal end of the tubule is the narrow 

 end-filament which is undoubtedly of a ligamentous nature 

 helping to support the ovaries in the abdomen. The tubule 

 may be divided into three zones depending on the character of 

 the cells present. At the proximal end is the nurse chamber, 

 containing all the nurse-cells. These stain very deeply and it 

 is impossible to make out their cell walls. The chromatin of 

 their nuclei is in the form of diffusely spread granules, and usually 

 there is present a chromatic nucleolus and a true plasmosome 

 (Fig. 45, n.c.). At the base of the nurse chamber (Keimlager) 

 are found numerous young oocytes in various stages of synapsis. 

 Proceeding distally from the nurse chamber are the older oocytes 

 of the post-synaptic stages, those farthest away from the nurse 

 chamber being the oldest and largest (Fig. 34, ooct. 2). In this 

 region are also found the follicle-cells (f.c.} which begin to form 

 definite follicles around the oocytes. As the young oocytes 

 begin to migrate distally from the base of the nurse chamber, 

 they still retain protoplasmic connections with the cytoplasm of 

 the nurse-cells, resulting in the formation of pseudopod-like 

 projections from the oocytes, the egg-strings (e.s.), by means of 

 which nutriment is passed from the nurse chamber to the oocytes. 

 Even old oocytes in which yolk is beginning to form still retain 

 connection with the nurse chamber by means of the egg-string 

 (Fig. 47). In the ovaries of young pupae the egg-strings appear 

 simply as cytoplasmic protrusions of the oocytes, but in the 



