NEMATOIDEA. | 351 
nally, such as the cellular membrane, and even in the thickness of 
the membranes and the parenchyma of the viscera; there we some- 
times find them in bundles and countless numbers, enveloped in spe- 
cies of capsules. They are found in Insects and their larve, and 
even in the visceral cavity of several Mollusca. The most celebrated 
species of this genus 
F. medinensis,Gm.; Encyc. 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 con- 
vulsions, according 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 dis- 
tinguishing character(1). 
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 
PT." dispar, Rud!s>> Getz.,* Vi51,°53) Eneyc., XXXII, 1, 
4. From one to two inches in length, of which the thickest 
portion forms but the third. This part, in the male, is spirally 
convoluted, and a little penis projects near the tail. It is 
straighter in the female, and simply perforated at the extre- 
mity. | 
It is one of the most common Worms in the great intestines 
of Man, where, in certain diseases, jt becomes prodigiously mul- 
tiplied(2). 
Naturalists have distinguished from the preceding the 
(1) For the other Filariz, see Rud., Hist., I, 57, Syn., p. 1. 
N.B. Rudolphi, in his Synopsis, has suppressed the genus Hamuxartra, 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. 
(2) For the Tricocephali of animals, see Rud., Ent., II, 86, and Syn., p. 16. 
