78 T. AIDA. 



show that the cells which constitute the stalk-— or stalk-cells as I shall 

 call them hereafter—are produced from the cells of the germinal epithe- 

 lium by a succession of amitotic divisions and fuse one after another 

 witJi the ovum until the latter becomes mature. 



We thus find two or three stalk-cells at the hase of a young ovum. 

 Fig. 1 is a cross section of the ovary of Sagitta bipunctata hardened 

 with Flemming's stronger solution. Each of the ova a and b has two 

 stalk-cells at its hase, where the germinal epithelium makes a deep inden- 

 tation, a is a nearly mature ovum and its cytoplasm shows a fine 

 cobweb structure. It has at its hase a large stalk-cell which appears 

 as a stopper to the spaceous indentation of the germinal epithelium 

 under the ovum, and an indication of another cell which has been ab- 

 sorbed by the ovum, b is a younger ovum and its cytoplasm is a dense 

 reticular mass. There is a distinct stalk-cell which has been taken up 

 by the ovum, and below it there is another which serves as the stopper 

 to the indentation in the germinal epithelium. This last cell is smaller 

 than the stopper cell of the ovum a, as .is also the indentation of the ger- 

 minal epithelium under it compared with the corresponding structure 

 under the ovum a. 



In order to show that these stalk-cells are produced from the ger- 

 minal epithelium by amitotic division a few of the nuclei undergoing 

 that process have been sketched, and are reproduced in fig. 2. We find in 

 the germinal epithelium two kinds of nuclei ; those belonging to the first 

 kind have each a looped varicose chromatic filament (fig. 2, b lower 

 nucleus) and lie generally in the deeper portion of the epithelium ; the 

 nuclei belonging to the second kind, which are found in the external 

 portion of the germinal epithelium (fig. 2, a, b, upper nuclei, c, d.), have 

 many dispersed chromatic particles and a central body of aggregated 

 chromatic substance containing in its center a nucleolus-like structure, 

 which can be well differentiated from the peripheral chromatic portion 

 by a double-staining with orange Gr and hematoxylin. The second 

 kind of nuclei is produced by direct division from the first class : a part 

 of the long looped chromatic filament is first constricted off as a round 



