Confribvtio/is to th; Shidy of tlu; Onf/enesw of ratell'i. lo 



\vould seem that not the least important part of their function 

 during oogenesis is the formation and storage of food for the develop- 

 ment of the embryo. Variations in their behaviour in different 

 organisms are most likely related to the different conditions of 

 niitrition to which the growing oocyte is subjected. Further 

 research alone will solve this problem of biology. 



SUMMA-RY. 



I. Nutrition of the Young Ooci/te. 



1. The young oocyte arising from an undifferentiated cell of 

 the germinal epithelium is surrounded by nurse cells containing 

 yolk granules. 



2. As the oocyte grows and extends outwards into the lumen of 

 the ovary it becomes surrounded by some of these nurse cells, 

 which form a temporary follicle. 



3. The yolk granules of the nurse cells are completely used up 

 in providing nourishment for the growing oocyte, and at quite an 

 early stage in its development the nurse cells disappear from its 

 surface. 



II. Golgi Apparatus and Vitelloyenesis. 



1. In the youngest oocytes the Golgi apparatus consists of a 

 number of curved rods surrounding the archoplasm. 



2. Probably in the archoplasm, yolk is formed under the in- 

 fluence of the Golgi rods, and while this is taking place other 

 Golgi elements divide and spread out in the cytoplasm, thns leading 

 to the formation of scattered yolk granules. 



3. The archoplasm breaks up and disperses in the cell. Probably 

 each Golgi element as it moves away from the archoplasm carries 

 with it a small portion of the latter, and this becomes distended 

 as the result of fatty yolk being formed within it. 



4. Scattered groups of Golgi elements continue the process of 

 volk formation until the egg is filled with spherical yolk bodies 

 surrounded by Golgi elements. 



5. When the yolk bodies are completely formed the surround- 

 ing layer of Golgi elements breaks up, and fragments pass out 

 into the cytoplaom and come to form a peripheral layer under- 

 neath the vitelline membrane, and another layer around the nucleus. 



(d. Throughout the process of yolk formation there is an extru- 

 sion of nucleolar material from the nucleus into the cytoplasm. 



