194 Harry Lewis Wieman. 



a large number of workers have yielded some interesting and impor- 

 tant data; but the theoretical deductions drawn from these data 

 have not been in all cases entirely justifiable. Attention has been 

 focussed on the chromosomes largely because they happened to 

 be objects made conspicuous by the readiness with which they 

 can be stained with certain dyes employed in cytological technique, 

 while other factors in heredity have been overlooked simply 

 because they are not expressed so clearly in a morphological form. 

 The chromosomes certainly have their place in hereditary proc- 

 esses, but the results of the present investigation indicate that 

 they are but the manifestation of properties which belong to 

 the cell protoplasm as a whole. 



IV. Summary 

 The Ovary 



The functional germ cells of the ovary and the nurse cells have 

 a common origin from the primordial germ cells. The configura- 

 tion of the latter in larval and pupal stages is such as to suggest 

 an amitotic division period of short duration. The nuclei at 

 this time are characterized by the presence of a basic staining 

 nucleolus in various stages of division surrounded by a clear non- 

 staining area. 



The epithelial cells are somatic cells derived from the meso- 

 dermic somites. During the larval and pupal stages the terminal 

 thread contributes epithelial cells to the egg chamber. In pupal 

 stages, the two regions become separated by a structureless 

 "limiting membrane" which develops first at the sides and finally 

 becomes continuous all the way across the ovariole. In the er- 

 lier history of the ovary, the relation of the epithelial cells to the 

 germ cells is such as to indicate a nutritive function for these 

 cells, but it does not appear that they enter into the formation of 

 the egg follicles. The view is here advanced that the latter struct- 

 ures arise from the cells of the ovariole stalk. In later stages the 

 epithelial cells are concerned in forming the delicate membranes 

 which enclose the cysts. The peritoneal sheath of the ovary, 



