ENCHYTR^ID^ IO7 



satisfied myself that this is not the case. In several instances I could 

 plainly see that the cilia were attached to the inner membrane. 



This can only be explained by supposing that the chylus canal is 

 simply an invagination of the ciliated surface of the cell, and that the 

 object of the cilia is to conduct the chylus as close as possible to the 

 blood sinus at the base of the chylus cell. By means of the canal a 

 much greater surface is exposed to the action of the intestinal juices, 

 and these juices can be quickly and surely brought to a close contact 

 with the blood. In this manner no diminution and weakening of the 

 intestinal wall is necessary, and the same object — that of rapid 

 absorption of the intestinal digested matter — is accomplished with a 

 thick and strongly built intestine. The bottom of the chylus cell rests 

 always on a basement membrane directly in contact with the blood 

 sinus. In order further to increase the contact surface the canal is 

 always bent, and part of it thus runs parallel with the blood sinus. In 

 some species the canal is not only bent, but it is branched and exhibits 

 the form of a bunch of canals, which form must still more facilitate the 

 absorption of the nutritive juice in the intestine. It is probable that 

 these cilia are present in all chylus cells, but it is also certain that they 

 do not extend to the bottom of the canals, but cease a certain distance 

 from the open mouth, generally extending only about half way down 

 the duct. When the canal is bent this bend projects toward the head 

 of the worm, which arrangement would facilitate the driving of the 

 chylus into the canal. 



For the various forms of the chylus cells of the respective species I 

 must refer to the description of these species. Here I will only state 

 that the form of the cells is quite varied and characteristic of the species. 



The inner lining of the cell is generally bounded on either side by a 

 more or less thick layer of granular cytoplasm. This layer reminds 

 me in many respects of the thick granular layer of the common epithe- 

 lial cells, which as is well known serves to shut out bacteria and pre- 

 vents other microbes from entering the cells. This granular laj^er in 

 the chylus cells probably serves the same purpose, though it may be- 

 sides have other properties, as for instance, those of a digestive nature. 

 In many species there is no distinct membrane lining the bottom or 

 lower part of the canal, and the granular la^-er seems to line the 

 lumen. But in some species there is a distinct lining which could not 

 readily be explained except by the theor}^ of invagination. Where the 

 lining is not present we may suppose that an absorption has taken 

 place in that part of the canal. Most of the chylus cells, as first 

 observed by Michaelsen {'S6), lean slightly toward the head of the 



