474 ENTOZOA. 



thick a& Uie barrel of a pigeon's quill. Its pointed and hooked tail constitutes 

 its distinguishing character*. 



TniCHOCEPHALUS, 



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 t lie 



T. dispar. Rud. ; Gffitz., VI, 1, 5 ; Encyt, XXXIII, 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. It is straighter in the female, 

 and simply perforated at the extremity. 



It is one of the most common worms in the great intestines of man, where, 

 in certain diseases, it becomes prodigiously multiplied f . 



Naturalists have distinguished from the preceding the 



ASCARIS, Linnceus. 



The Ascarides have a round body, attenuated at each extremity, and a 

 mouth furnished with three fleshy papilla?, between which an extremely short 

 tube occasionally projects. This genus is very numerous in species which 

 are found in all kinds of animals. Those which have been dissected pre- 

 sented a straight intestinal canal, and the females, by far the greater number, 

 exhibited an ovary with two branches, several times the length of the body, 

 opening externally by a single oviduct, near the anterior fourth of the total 

 length of the animal. 



Two white threads, one of which extends along the back, and the other 

 along the belly, are considered by Messrs. Otto and Cloquet as the nervous 

 system of these animals ; two other and thicker threads, one on the right and 

 the other on the left, are considered by some as muscular, and by others as 

 vascular, or even as tracheae. 



STRONGYLUS, Muller, 



Where the body is round, and the anus of the male is enveloped by a sort of 

 bursa, variously shaped, from which issues a little thread that appears to be an 

 organ of generation. These two last characters are wanting in the female, 

 which has sometimes caused her to be taken for an Ascaris. 



* For the oilier Filarisc, sec Rud., Hist., ii. 57, Syn., p. 1 . 



N.B. Rudolph!, in his Synopsis, has suppressed the genus HAMULAIUI, which was 

 characterised by two little oval filaments. On examination, they were found to be the 

 male organs of generation, placed at the posterior extremity. 



f For the Trichocephali of animals, see Rud , Ent., ii. 8fi, imd Syn., p. 16. 



