192 EDWIN S. GOODKIOH. 



canal, where it is contiaued for some length,,^. Undulations 

 swiftly pass along the flagellum from its base to the free end 

 in the canal. 



The protoplasm of the tube-bearing cells is very granular, 

 many of the granules being probably of an excretory nature. 

 At the distal curved end of the neck are generally seen delicate 

 protoplasmic projections, often of great length, floating in the 

 coelomic fluid, pr. These are not cilia, but appear to be rather 

 of the nature of amoeboid processes. I have not observed 

 them moving. The tube itself is rather narrower at its base 

 than at the end which enters the canal. It is quite straight 

 as a rule, and oval in section. The wall is composed of a clear 

 refringent substance, apparently of a cuticular nature, which 

 resists the action of caustic potash longer than the proto- 

 plasmic parts of the cell. 



The large oval nuclei (figs. 26 — 29, n.) have in the fresh 

 tissue a vacuolated appearance. They are remarkable for the 

 extreme avidity with which they take up ordinary nuclear 

 stains, such as carmine or haematoxylin. So pronounced is 

 this tendency that in a preparation or section they become 

 deeply stained when the other nuclei are hardly yet affected, 

 and become intensely overstained by the time the other nuclei 

 are sufficiently coloured (see fig. 25, term. pi. neph.), A stained 

 preparation of a whole branch of the terminal plume, some- 

 what flattened out, is figured (fig. 29), showing the nuclei closely 

 packed in an irregular double row. 



So far as I have observed the tube-bearing cells are never 

 placed singly, but are ranged in pairs along each side of the 

 canal (fig. 28). The bases and necks of two adjacent cells are 

 closely applied to each other along one side to near the distal 

 extremity, where they diverge to form the terminal crooks. 

 Although the cells are thus firmly fixed to each other, yet a 

 clear line of demarcation can always be detected separating 

 them along the middle line. Occasionally three cells are joined 

 together, as shown in the middle of the branch in fig. 26. 

 The nephridia occur throughout the body of the worm, ex- 

 cepting in the first and last few segments. 



