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this respect, that they seem to vie with the almost ubiquitous 
Diatomacese, with which they are often found associated. 
Elsewhere* I have thus enumerated some of the situations in 
which they are to be met with : Beginning with the land and 
freshwater species, I have found them in all the specimens of 
soil examined, in moss, in various species of lichen, about the 
roots of fungi, also in the roots of grasses and between the 
sheaths of their leaves, amongst the mud of ponds and rivers, on 
the freshwater Algge, amidst decaying liverworts and mosses, 
and on submerged aquatic plants. The marine species exist in 
great abundance in the surface mud of rivers and estuaries,f in 
the sand and amongst the small stony debris under the shelter 
of rocks, as well as in the tide pools, where they swarm about 
the roots of the corallines and on some of the smaller and finer 
sea-weeds, especially those having a dingy appearance from the 
presence of Diatomacese. And lastly, two or three species I 
have found as pseudo-parasites, within the substance of some of 
the softer sponges.” 
These animals, so far as I have seen, have varied in size 
between tV of an inch and J of an inch in length, though some 
of the marine forms only have attained the latter dimensions. 
The largest freshwater species, Dorylaimus stagnalis, is about 
one-third of an inch long. They are all remarkable for the 
glass-like transparency of their integuments, so that their 
internal anatomy can be easily ascertained by microscopical 
examination. 
Although much difference exists with regard to the activity 
of different species — some being slow and tardy in their move- 
ments, whilst others are notably the reverse — still the mode of 
locomotion is very similar in all. This is mostly effected by 
eel-like undulations of the body, such as at once distinguish 
these animals from the Naiclinim, and from Annelids generally. 
At other times they glide and twine, serpent-like, amongst the 
branches of the aquatic plants or algae which they frequent, 
and occasionally they anchor themselves firmly by means of a 
caudal-sucker with which very many are provided, and con- 
tinue for some minutes swaying about in all directions, or 
darting their bodies hither and thither with the greatest 
rapidity. J 
* Monograph on the AnguilluKdcB or Free Nematoids, Marine, Land, and 
Freshwater, with descriptions of 100 New Species. Trans, of Linn. Soc. 
(1865), vol. XXV. 
t I have found six different species existing more or less abundantly in a 
small portion of mud that could be held on a shilling piece. 
% The best method of detecting and capturing these animals is given at 
p. 92 of my Memoir in the Trans, of Linn. Soc. 
