76 MR. H. CHARLTON BASTIAN’S MONOGRAPH 
in general. Since, however, the announcement of the discovery of so many free Nema. 
toids is likely to suggest to the minds of many the belief that these are identical with 
the parasites, being merely the revelation of another stage of their life-history, which 
has hitherto been hidden from us, it seems desirable to bring forward some evidence to 
disprove such a supposition, and establish the claim of these minute creatures to a distinct 
and independent place in the animal kingdom—and more especially so since precisely 
such a view has been taken by one of the principal writers on these free Nematodes, For, 
at the conclusion of his paper before mentioned, Carter, speaking of the uncertainty still 
existing with regard to the early history of the Dracunculus, adds, ** Tt remains à sub. 
ject for future and interesting inquiry, but not more so than the still further elucidation 
of the Filaridæ generally, both free and parasitic; for when we consider that the former 
abound in species, and are spread in myriads probably all over the world, where there is 
vegetable matter for them to feed upon, in salt as well as in fresh water, in the sea and 
on the land, while the latter inhabit all animals, perhaps, more or less, down to the 
lowest worms; that many of the former’ leave their habitat and vegetable food for a 
temporary residence in animals, to live thus on animal food, and that therefore the whole 
of the parasitic forms may be originally derived from the Jree ones ” ; for these, and other 
reasons, he says, “these worms, at first apparently insignificant from their thread-like 
form and scarcity, are seen to assume an importance in organic creation which calls for 
a much more extended study of them than they have as yet received” (p. 112). 
With the view of investigating this question, I made a careful analysis of the anato- 
mical details and plates given by Dujardin, in his * Histoire naturelle des Helminthes, 
of the N ematoid Entozoa,—selecting this writer, not only on account of the more com- 
plete descriptions found in his work, but also in deference to his extensive practical 
acquaintance with this particular branch of his subject. The result of this examination 
has sufficed to convince me that the nearly constant combination of several important 
characters—so universal as to be typical of these free Nematodes—are only probably 
present in two or perhaps three of the parasitic genera. These distinct characters arè 
furnished by the male and female genital organs,—the males having two equal sub- 
terminal intromittent spicules, 
the vulva situated at about the middle of the body, a short vagina, with a symmetrical 
whose branches lie on opposite sides and are connected with a short and 
erus remains aborti ; : aii 
retains its sr in ed (PI.X. fig. 113), whilst the anterior segme 
n referring to Dujardin’s classification it will -— ho Isa maiigi ii 
ee Seven sections, together with an appendix containing the little-known or 
c ns iiid anatomy of the animals included in his first section, re 
NGC strictiy saida he "ichosoma, 1s totally distinct as regards the Mi 
in reality to a nearly allied order, miden ie 5 rie to, constituting the mM vete puce: belong 
