Nucleoli during- the Oogenesis of the Dragon-fly. 221 



along the linin reticulum to all points of the nucleus until a heav}' 

 reticulum of chromatin is again formed (Fig. 60 — 63). In this form 

 there is no indication that oxyphile and basiphile substances are 

 derived from one another. 



(b) Yolk-nuclei. 



The formation of yolk-nuclei is practically the same as in 

 Plaihemis. In the germinal area, while the chromatin is being 

 collected around the nucleolus, a layer of basiphile granules is left 

 around the periphery of the nucleus (a in Fig. 44, 46 and 50). At 

 "the same time, a mass of granules is deposited just outside the 

 nucleai membrane (Fig. 39—44), and then gradually moves away 

 from the nucleus to break up and scatter through the cytoplasm. 

 As in later stages (Fig. 54 and 55) nothing is seen of the layer of 

 chromatin just inside the nuclear wall, one may conclude that it 

 has passed out to form the yolk-nucleus. Here, as in Plathemis. I 

 have never seen chromatin-granules passing through tlje nuclear 

 wall, and the chromatin, therefore, if it does pass out, must do so 

 in solution. 



The granules of the yolk-nuclei scatter through the cytoplasm 

 earlier in Anax than in FlatJwmis. so that in the later growth-period 

 yolk-nuclei are seldom seen. 



VI. Summary. 



1. The ovaries of Anar and Plathemis are identical in structure 

 except in the late growth period, at which time the nucleoli show^ 

 striking differences. They are made up of an immense number of 

 egg- strings. 



2. Each egg-string shows three well marked regions, end-fllament. 

 germinal area and growth area. The strings are attached in front 

 to the dorsal ligament, and extend backwards and outwards to the 

 oviducts. 



3. The cells of the end-filament give origin to both follicle-cells 

 and germ-cells. 



4. Follicle-cells throughout the extent of the egg-string exhibit 

 the same structure as the filament-cells, showing lightly staining 

 cytoplasm, oval nuclei with little chromatin and a single oxyphile 

 nucleolus. 



