144 ZOOLOGY 



(Fig. 63, A). They are set free, however, and perform no visible 

 function, and eventually drift down the tail with the surplus 

 protoplasm (Fig. 63, F, G). 



In Abraxas and Cavia they are first found very near the Golgi 

 apparatus, and possibly have been extruded from it (Figs. 65, 

 QQ, A). Throughout the divisions and subsequent spermateleosis 

 they keep close to the Golgi apparatus, and even as the Golgi 

 remnants drift down the tail the vacuoles can be seen in company 

 with them (Figs. 65, 66, F, G). 



They have been described as the Y-granules in Saccocirrus (33), 

 with similar behaviour (Fig. 62, A). No function can be attributed 

 to them as yet. They have also been observed by Voinov (131) 

 and Hirschler (52, 53). 



Oogenesis and Yolk Formation. Oogenesis, apart from the 

 deposition of reserve products, is comparatively uneventful. This 

 deposition occurs before the first oocyte division during the so- 

 called growth period. Simultaneously the nucleus enlarges after 

 synapsis, becomes very lightly staining, and is termed the 

 germinal vesicle. This is a comparatively long period. The 

 separation of three polar bodies by unequal division occurs finally. 

 Fertilisation may occur at many stages of the maturation division, 

 but a very remarkable case is reported in Saccocirrus (Gatenby), 

 where it takes place before the germinal vesicle stage. By far the 

 most interesting period of oogenesis is that of yolk formation, and 

 to that we shall now turn. 



Just as the formation of the acrosome by the Golgi apparatus 

 in spermatogenesis proved to be a sure starting point for investi- 

 gating the problems of the Golgi apparatus, so it was hoped that 

 a study of vitellogenesis in oogenesis would lead to further light 

 being thrown on the functions of the various cell organs. The whole 

 matter has, however, proved to be of extraordinary complexity, so 

 that there are few fields of cytology in which there is more confu- 

 sion, and opinions are more hopelessly divided. The study of yolk 

 formation has increased greatly during this decade, and a convenient 

 starting point will be found in a paper by Gatenby and Woodger 

 in 1920 (41), in which they summarise the position at that time. 



Their review includes a description of the vitellogenesis of three 



