No. 4.] HIRUDINEEN STUDIEN. 2 I 3 



pressed under a cover glass while living, and it was found that 

 the shape of the nephridium adapts itself to the shape of the 

 spaces left free by the surrounding tissues. It is impossible 

 and idle to establish morphological types of nephridia for the 

 different genera of leeches. 



The vesicula terminalis is lined by an epithelium-bearing cilia 

 on the inner surface. The canalis terminalis is to be regarded 

 as a simple invagination of the epidermis. 



The anatomical investigation was almost exclusively prose- 

 cuted on living material, partly on very young uninjured ani- 

 mals, partly by the study of rapidly made dissections and 

 teased preparations. This was of paramount importance in 

 order to gain perfectly trustworthy results and to eliminate the 

 subjective interpretation of reconstructions from sections. This 

 anatomical investigation was finished in all its details in the 

 fall of 1894, and all the drawings pertaining to this part of 

 the work were executed in Wood's Roll during the summer of 

 1894. 



In the fall and winter of 1894 the investigations concerning 

 the pigment formation and origin of markings were finished, 

 and in the spring and summer of 1895 the greatest part of the 

 cytology of the nephridium was worked out. 



II. 77/t- Cytology of the Excretory Organs. 



New points were gained with regard to the finest structure 

 of the ciliated cell by the study of the ciliated crown cells of 

 the funnel. 



The cilia were found to consist of three parts, a basal piece 

 staining deeply with haematoxylin, a middle piece staining very 

 faintly with the same agent, and the flagellum or cilium proper 

 staining with the acid anilins, e.g., Bordeaux red. The basal 

 piece is rod-shaped, and stands not quite vertically to the cili- 

 ated surface, but a little inclined. The middle piece is more 

 round, and it seems as if the middle pieces of one row of cilia 

 touched each other. The flagellum is thin, very long, and 

 elastic, and is regarded by the author as a passive material, a 

 metamorphosed protoplasm, like a secretion. 



