1919] Riickes: Male Genital System in Lepidoptera 203 



have a tendency to round off. Whether this change has 

 anything to do with the secretory activity of the cells the 

 author is not prepared to say. The activity of the nucleolus 

 was not studied. At any rate, there is a very evident change in 

 the character of the chromatin. 



Continuing a step further, we get a condition represented by 

 Figure 12. The rapidly elongating cells crowd over one 

 another, and we have the formation of a little nest-like mass of 

 cells. The function of the nidus in the epithelium of the 

 digestive tract is to replace cells, as they are cast off into the 

 lumen. As far as was determined in the vas deferens, there is 

 no migration of the cells into the lumen, and therefore these 

 groups of cells should be called pseudo7iidi. The vacuolization 

 continues, and the chromatin now appears as large granules. 

 The nuclei remain round or oval and centrally placed. 



There is a gradual, but very prominent growth of the cells 

 in the vas deferens from now on till we reach the end of the 

 pupal period when several changes take place rather rapidly. 

 The pseudonidi become very prominent, and the contour of 

 the lumen becomes markedly rigid, as figured in Fig. 16. The 

 muscle layer has been formed and outside of it is the peritoneal 

 membrane. The most striking feature of this stage is the 

 structure of the epithelial cells (Fig. 12). They have become 

 totally vacuolate, and throughout the cytoplasm occur promi- 

 nent, deep staining particles that are evidently secretion 

 droplets; where these particles come from has not been 

 determined. The nuclei migrate to the periphery of the cell 

 and become quite large, but the chromatin appears in very fine 

 granules, producing a condition that does not differentiate the 

 nucelus very well from the rest of the cell. The nuclei assume 

 the shape of the cell. Between the muscle layer and the cells 

 is a prominent basement membrane. 



The condition of the cells at the time of the emergence of the 

 imago may be represented by Fig. 14. The number of secretion 

 granules is reduced, but we have in the lumen of the duct, a 

 whitish liquid containing also an abundance of sperms. This 

 is the seminal fluid and has been produced by the cells of vas 

 deferens. The lower portions of the cells show a peculiar 

 fibrous condition of the cytoplasm. This is very difficult 

 to illustrate. The tips still show prominent vacuoles. 



