408 ENTOZOA. ELMINTHOGAMA. 



Gen. PLANARLE, Bosc. 



Body oblong, flattened, semigelatinous, very contractile, gene- 

 rally simple, sometimes furnished anteriorly with two auricu- 

 lar appendages ; two openings under the belly. 



The genus Planaria of authors has received much elucidation from the experi- 

 ments and observations made by John Graham Dalyell, Esq. on the living animals, 

 the results of which were published in 1814, under the title of Observations on Pla- 

 narice. In this interesting volume, Mr Oalyell states his investigations as leading 

 him to characterize these animals as forming two divisions, the first of which may 

 be defined, " Naked, flattish, in a state of abstinence, provided with a proboscis pro- 

 truded from the middle of the belly or under surface ; swimming supine." The 

 second division is thus defined : " Body in a state of repletion resembling a double 

 cone, mouth in the anterior extremity." The work is illustrated by coloured plates. 



FAMILY II. LOMBRICOJDA. 



Worms living in the interior of the bodies of other animals, and 

 destitute of appendages representing antennas or feet. 



TRIBE I. ANODOXTA. Nematoides, Rudolphi. 

 Body generally filiform, with the mouth often orbicular, always 

 deprived of hooks or spines, but with lips, papillae, or a small 

 naked tube in the form of a proboscis. 



I. Posterior extremity of the body not terminating in a bag or bladder. 



1. Mouth not tubular. 



A. Mouth not covered by a striated hood. 



Gen. FILARIA, GORDITJS, TRICHOSOMA, TRICHOCEPHALUS, OXYURUS, 

 OPHIOSTOMA, (Fissula, Lam.;) ASCARIS, SPIROPTERA. 



a. Body furnished with lateral hairs. 

 Gen. TUBIFEX, STYLARIA, NAIS. 



B. Mouth covered by a striated hood. 



Gen. CUCULLANUS. 



2. Mouth in the form of an exsertile tube. 



Gen. LIORYNCHUS. 

 1 1. Posterior extremity of the body in the males in the form of a bag or bladder. 



Gen. PHYSALOPTERA, STRONGYLUS. 



The species of the genus Filaria have a slender elongated body in the form of a 

 thread, with a round mouth at the anterior extremity. They are found chiefly in 

 the interior of animals, in the cellular substance, in the muscles, and in the paren- 

 chyma of the viscera. The most celebrated species is the F. Medinensis of Gmelin, 

 very common in warm countries, which insinuates itself under the human skin, 

 principally of the legs, and often occasions serious injury. It is sometimes found 

 ten feet in length. It is extracted by slow degrees for fear of breaking in the 

 wound ; and the negroes are very dexterous in thus withdrawing it. The distinc- 

 tive character is to have the end of the tail pointed or bent. A species of the ge- 

 nus Gordius, (G. aquations of Linnaeus,) frequently found in Britain in still wa- 

 ters, not thicker than horse-hair, is popularly considered in many parts of the 

 country to be a hair of that description in the act of being transformed into an 

 eel. Cuvier, it may be remarked, places the genera Gordius, TuUfex, Stylaria, 

 and Nais of Lamarck in the class of Annelides, while the latter author thinks their 

 proper place is among the worms. The limits of the two classes indeed are not 

 well determined, and can only be ascertained by minute anatomical investigation. 

 The genus Ascaris is found in the interior of many animals ; and one species, the 

 A. lumbricoides of Lin., is found without any sensible difference in man, the hor&e, 

 the ass, the ox, and swine. It is sometimes found fifteen inches long ; and when 

 multiplied to excess in the visceral cavities, oiten occasions serious disease. 



