THE GERM-CELLS OF CICADA (TIBICEN) SEPTEMDECIM. 433 



can nurse cells be found in various stages of disintegration, but 

 the products of such disintegration can actually be seen to pass 

 down the egg-strings to the oocytes. From Fig. 45, the impres- 

 sion may be gathered that the material derived from the dis- 

 integrated nurse cells passing down the egg-string is accumulated 

 in a zone about the nucleus. Such, however, is not the case and 

 as will be shown later, the deeply staining perinuclear zone 

 consists of mitochondria and in material fixed in Bouin's fluid, 

 the mitochondria disappear while the granules in the egg-string 



are preserved. 



3. Mitochondria in Oogenesis. 



(a) Mitochondria in Growth Stages. The young oocytes of 

 Cicada lying at the base of the nurse-chamber are at all times 

 distinguishable from the nurse-cells not only by their character- 

 istic nuclei, but also by the presence of definite aggregations of 

 granular mitochondria which are characteristically localized in 

 the cells. 



During the entire synaptic period of the oocyte, the mito- 

 chondria are found lying in the cytoplasm as a cap of deeply 

 staining granules closely applied to the nuclear membrane at 

 one pole (Plate V.). As will be seen from Figs. 38, 39, 40, the 

 pole of the nucleus at which the mitochondria are found always 

 corresponds to the pole of the nucleus towards which the synaptic 

 threads are polarized. It will at once be seen by comparing 

 Figs. 17 and 40, that the mitochondria of the oocyte and sperma- 

 tocyte are localized in the cytoplasm at homologous positions, 

 namely at the side of the nucleus where the idiozome, the sphere 

 or centrosome is probably located. In the oocytes, however, 

 no centrosome or sphere can be distinguished and similarly 

 Montgomery ('n) states that in Euschistus "it is not clear 

 \vhether this body (idiozome or sphere) has any homologue in 

 the oocytes," etc. 



The mitochondria of the oocytes of Cicada are always in the 

 form of granules, never assuming the filar form as found in the 

 spermatocytes. During the later synaptic stages (pachytene 

 stage, Fig. 40) there is an increase in the amount of mitochondria, 

 but their localization at one pole remains constant. In the 

 post-synaptic stages we find that, although the mass of mito- 



