NEMATO1DEA. 473 



ORDER I. 



NEMATOIDEA, Rudolphi*, 



THIS order comprises those whose external skin, more or less furnished with 



muscular fibres, and usually striated trans- 

 versely, contains an abdominal cavity in 

 which is a distinct intestinal canal, extending 

 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 numerous threads, considered by some 

 writers as vessels for the conveyance of the nutritious fluid, and by others as 

 tracheae, 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 oesophagus is 

 frequently smaller, and in some species we remark a larger and more vigorous 

 stomach. The internal organs of generation consist of extremely long vessels, 

 containing the semen or the ova, which open at different points, according to 

 the genus. 



FILARIA, JLinnaus, 



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

 extremity by a round oral aperture. The Filariee 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 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, 

 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 



* This order, with the exception of the two last genera, constitutes the ENTOMOZAIRE 

 AroEs OXYCEPHALES of M. de Blainville. 



