NEMATOIDEA. ^5 



from the moxath to the anus, and wliere we generally observe distinct 

 organs in each of the sexes. The intestine is connected with the 

 neighbouring jjarts, 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 tracheiB, but without any 

 l^roof 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 AVe 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. 



F[LARIA, Lin., 

 Where the body is elongated, slender, filiform, and perforated at the 

 anterior extremity by a round oral aperture. The Filariae in their 

 external appearance are very similar to the Gordii. They are chiefly 

 found in those cavities of animals Avhich 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 larvae, and even in the visceral 

 cavity of several Mollusca. The most celebrated species of this 

 genus, 



F. medinensis, Gm.; Encyc. XXXIX, 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*. 



Tbichocephalus, 



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.; Goetz., VI, 1, 5; Encyc, XXXIII, I, 4. 

 From one to two inches in length, of which the thickest portion 



* For the other Filariae, 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 

 he the male organs of generation, placed at the posterior extremity. 



