Contrilmtions to the Stud n of the Oogenesis of ratella. 7 



which are seen moving away from the archoplasm in fig. 4 multiply 

 by fission and spread throughout the cytoplasm. As they do so 

 they lead to the formation of yolk spheres. The archoplasm also 

 seems to break up into several portions, each of which becomes an • 

 active centre for the formation of yolk and the spread of baton ettes 

 which carry on the same process. In fig. 8, which is drawn under 

 a lower power than fig. 7, several such groups of yolk bodies are 

 seen, as are also scattered elements which are forming yolk bodies. 



It is during the early stages of this process of the spreading 

 out of the Golgi apparatus and yolk formation that a peculiar 

 nuclear phenomenon is to be observed. The large plasmosomes to 

 which attention was directed in the youngest oocytes, fragment 

 under peculiar conditions, and there is during subsequent stages 

 an emission of nucleolar material. This is shown in fig. 6 and 

 fig. 8. The exact nature of this process I am still investigating, 

 and hope to describe later. 



Gradually the Golgi batonettes spread throughout the cyto- 

 plasm. At fig. 5 is shown a cell in which they are much dispersed. 

 The yolk bodies appear colourless, as all the fat has been dissolved 

 out. If the fat is not removed from the cell, but is stained with ' 

 osmic acid, the eggs at this stage appear as shown in fig. 9. This cell 

 shows the gradual formation of fat under the influence of the Golgi 

 elements. At GE.l are seen single batonettes. At GE.2 several 

 are seen together, and between them the cytoplasm stains a dark 

 colour. At GE.3 the yolk body has increased in size and the 

 Golgi elements have spread out over its surface. From the 

 examination of various eggs at this period of growth it seems that 

 the Golgi batonettes come to almost completely surround each 

 yolk sphere. When fully formed the yolk bodies stain a deep 

 black with osmic acid, as seen at GE.4 and at Y. in fig. 10. 



It is impossible to say with certainty whether the fatty sub- 

 stance of the yolk bodies is formed within the archoplasm or in 

 the cytoplasm. Owing to the manner in which the apparatus as a 

 whole stains black when the dispersal of the batonettes commences, 

 it seems that this must be due to the archoplasm becoming laden 

 with fat ; but the case of those yolk spheres which are formed 

 under the influence of scattered batonettes is very difficult to 

 settle. It may be that each batonette as it leaves the archoplasm 

 carries away a small portion of that substance, which grows and 

 becomes swollen with fat, but it is impossible to verify this from 

 my preparations. 



New yolk bodies continue to be formed throughout oogenesis. 

 At fig. 10 is shown a portion of the periphery of an egg at an 

 advanced stage of development. Many of the yolk spheres are 

 completely formcjd, but others are to be distinguished at various 

 stages of growth, and there are also scattered batonettes. 



The successive stages in the development of the yolk bodies are 



