NEMATOIDEA. 405 
from the mouth to the anus, and where we generally observe distinct 
organs in each of the sexes. The intestine is connected with the 
neighbouring parts, and the general envelope of the body by numer- 
ous threads, considered by some writers as vessels for the conveyance 
of the nutritious fluid, and by others as trachewe, but without any 
proof of the fact. It is impossible to detect any true circulation in these 
animals, but in several there appear to be one or two nervous cords 
arising from a ring which surrounds the mouth, and extending the 
whole length of the body along the internal surface of the envelope. 
The intestine is generally straight, and tolerably wide; the eso- 
phagus is frequently smaller, and in some species we remark a larger 
and more vigorous stomach. The internal organs of generation con- 
sist of extremely long vessels, containing the semen or the ova, which 
open at different points, according to the genus. 
Friuarta, Lin., 
Where the body is elongated, slender, filiform, and perforated at the 
anterior extremity by a round oral aperture. The Filariz in their 
external appearance are very similar to the Gordii. They are chiefly 
found in those cavities of animals which do not open externally, such 
as the cellular membrane, and even in the thickness of the membranes 
and the parenchyma of the viscera; there we sometimes find them in 
bundles and countless numbers, enveloped in species of capsules. 
They are found in Insects and their larvee, and even in the visceral 
cavity of several Mollusca. The most celebrated species of this 
genus, 
F. medinensis,Gm.; Encye. XX XIX, 3 (The Guinea Worm), 
is very common in hot climates, insinuates itself under the skin 
of man, generally that of the leg, where, if credence be given 
to the reports of certain authors, it acquires a length of ten feet 
and more, may remain there several years without producing 
violent pain, or cause intense agony and excite convulsions, ac- 
cording to the nature of the part it attacks. When it shows 
itself externally, it is seized and extracted very slowly, for fear of 
breaking it. It is about as thick as the barrel of a Pigeon’s 
quill. Its pointed and hooked tail constitutes its distinguishing 
character*. 
‘TRICHOCEPHALUS, 
Where the body is round, thickest posteriorly, and as slender as a 
_ thread anteriorly. This slender part is terminated by a round mouth. 
The most common species is the 
T. dispar, Rud.; Geetz., VI, 1, 5; Encyc., XXXIII, 1, 4. 
From one to two inches in length, of which the thickest portion 
* For the other Filariz, see Rud., Hist., II, 57, Syn. p. 1. 
N.B. Rudolphi, in his Synopsis, has suppressed the genus HAMULARIA, which 
was characterized by two little oval filaments. On examination, they were found to 
be the male organs of generation, placed at the posterior extremity. 
