Io6 EISEN 



small, between prostomium and somite I. Large dorsal pores in the 

 center of each somite, beginning with VII. Two kinds of lympho- 

 cytes. PejDtonephridia present. Esophagus gradually merging into 

 the intestine. Dorsal vessel rising posterior to clitellum. Blood col- 

 orless. Spermatheca generally with globular diverticles at the base of 

 the ampulla. Sperm-ducts comparatively narrow and long. Penial 

 bulb without interior muscular strands (^Lumbricillus bulb). Nephri- 

 dia with large anteseptal. Brain posteriorly and anteriorly convex. 

 The intestine in the vicinity of clitellum contains specialized chylus 

 cells. 



DETAILED DESCRIPTION. 



Chylus cells. — The most interesting feature in the anatomy of 

 Fridericia is undoubtedly the presence of chylus cells. These were 

 first discovered and described by Michaelsen ('S6). Michaelsen states 

 that he could not find that the ducts passed from one cell to another. 

 He further states that the cell walls were always indistinct and could 

 not be made out. Even in my own sections I find that the cell walls 

 are generally not very distinct, still I have succeeded in most instances 

 in making them out. I have also, satisfactorily to myself, demon- 

 strated that the canals are indeed entirely confined to a single cell. 

 They never pass from one cell to another. The chylus cells occupy 

 constant somites in the same species, and good species characters may 

 be had from their location, form and size. 



The intestine in these somites is lined by a layer of epithelial cells, 

 which are of different size and form in the respective species. Be- 

 tween these epithelials open the chylus cells into the intestine. The 

 chylus cells are generally long and narrow, broader at the bottom than 

 at the apex. They are perforated by a single canal which opens at 

 the apex of the cell and from there continues to the base of the cell, 

 then generally bending or even branching out. The nucleus of the 

 cell is generally situated not far from the base of the cell, in an angle 

 of, but outside of, the canal, where it is bent on itself. The canal is 

 somewhat different in different species. In most species the inner 

 surface of the canal is lined only by a thick layer of cytoplasmic 

 granules. But in some species there is a real lining membrane con- 

 tinued from the mouth of the cell to the base. In others this lining 

 membrane can only be traced a little way down. But the most inter- 

 esting part is that this inner membrane is actually covered with cilia. 

 At first I concluded that these cilia were accidental ones which had 

 been carried into the canal of the cell with the chylus from the intes- 

 tine, being digested in the cell together with the chylus. But later I 



