81 MR. H. CHARLTON BASTIAN'S MONOGRAPH 
dine, with whom they are frequently associated, and also from the Annelids generally. 
Other movements of the aquatic species may be well seen if these animals are placed in a 
watch-glass and examined by a low power of the microscope, when they may be observe 
twining amongst the branches of the aquatic plants or aleve which they frequent, their 
gliding movements suggesting a resemblance to tiny serpents, till the delusion is banished 
by a sudden change in their method of proceeding, when, anchoring themselves firmly 
by means of their caudal sucker, they continue for some minutes swaying about with the 
greatest rapidity, darting their bodies hither and thither, and bending in all directions, 
With respect to food, the free Nematodes seem to be almost exclusively vegetable 
feeders, though it is not often easy to recognize anything definite within their ali. 
mentary canal—the usual contents being a kind of granular débris, and in seven] 
species large oil-globules. In individuals of the genera Cyatholaimus and Spilophora, 
however, I have frequently seen the intestine filled with large Diatomacex, whilst in 
interesting in a physiological point of view, as an exemplification of the almost direct 
conversion of cellulose into fat and other products. In Dorylaimus stagnalis these large 
beads of fat are generally of a bright yellow, whilst in other species I have occasionally 
found them of a pure emerald-green colour, and in one instance even of a distinct magenta 
hue; but in the majority of species the fat is colourless. I have never yet seen one 
of these animals swallow a particle of food; but what they do take appears to remain 
a long time within the intestinal canal, becoming slowly and almost entirely metamor- 
phosed into fat, as the primary stage of assimilation. In this respect they differ notably 
from the Naidine, with which they are usually associated in both fresh- and salt-water 
mud; for with these, as with their near ally the Earthworm, the intestinal canal may be 
: ich seems borne out also by the thread-like dimensions 
of the cesophageal canal in the genus Tylelenchus. The so-called gastric teeth met with 
mm some of the free as well as the parasitic N ematodes, in the terminal dilated portion of 
