Nucleoli during the Oogenesis of the Dragon-fly. 2Và 



Avhere cut. To show the origin of the nucleoli in the germinal 

 area and the finer structure of the cytoplasm, very thin sections, 

 three to four micra, were needed. In the very large eggs, sections 

 as thick as ten micra were found to be advantageous in counting 

 the number of nucleoli and in studjing general relations. 



IV. The Ovaries. 



In Anax and Fhdhemis the ovaries are almost identical in shape 

 and general structure, so that one description will suffice for both 

 forms. They are elongated bodies, placed one on each side of the 

 digestive tract near the dorsal body-wall. In front they lie close 

 together but diverge as they pass backwards. They are spindle- 

 shaped, rounded off in front but tapering posteriorly, where they end 

 in the thread-like oviducts. 



Each ovary is made up of a large number of egg-strings, bound 

 together by peritoneal epithelium, which surrounds not only the 

 ovary as a whole but passes also between the egg-strings, making 

 a sheath for each. The egg-strings narrow anteriorly into delicate 

 threads, the end-filaments, which pass forwards and inwards, and 

 those from all the separate strings unite to form a supporting liga- 

 ment which lies just beneath the dorsal blood-vessel (cf. Daiber, 

 1904). From the ligament the egg-strings pass obliquely backwards 

 and outwards to the oviduct which runs along the outer margin of 

 the ovary. 



V. The Egg-strings. 



With respect to both the gross and minute structure until th& 

 growth period is reached, the egg-strings of Anax and Plathemis 

 are so much alike that, as in the case of the ovar}-. one description 

 is all that is necessary. Even in the later stages, the only 

 differences found are in the form and behavior of the nucleoli, and 

 these will be described separately for each form. 



Each egg-string consists of a row of germ- cells placed end to 

 end, attached in front by the end filament to the dosai peri- 

 toneum and extending outwards and backwards to the oviduct. As 

 mentioned in the description of the ovary, each egg-string is 

 surrounded by a layer of much flattened cells continuous with the 

 peritoneum (« in Fig. 1 and 39). Closely applied to the ovum itself 



14* 



