406 ENTOZOA. 



similar in form to those of this class, it is arranged along with 

 this division, though it does not inhabit the interior of an- 

 other species. 



Linnagus arranged this group 'of animals in a division of 

 his great class Vermes, including the genera Lumbricus, Si- 

 punculus, Fasciola, Gordius, Ascaris, Hirudo, and Myxine. 

 Subsequent writers, such as Pallas, Muller, Blumenbach, Bloch, 

 and Goeze, established new genera or added new species ; and 

 more lately, Cuvier, Lamarck, Rudolphi, and Bremser, from 

 more detailed examination of the animals, and a more intimate 

 knowledge of their structure, have proposed arrangements better 

 suited to the present state of the science. M. Lamarck divides 

 the class into three orders, viz. HISPID.E, RIGIDUL.E, and MOL- 

 LASS.E, the last of which is subdivided into three sections. In 

 the method of Cuvier the class forms two orders, LES CAVI- 

 TAIRES, and LES PARENCHYMATEUX, according to the struc- 

 ture of their body. And Rudolphi, in his work entitled Ento- 

 zorum sive Vermium Intestinorum Historia Naturalis, arran- 

 ges them into five orders, viz. J . NEMATOIDES : Body elon- 

 gated, cylindrical, elastic. 2. ACANTHOCEPHALUS : Body cy- 

 lindrical, slightly elastic, with an anterior simple or compound 

 prolongation covered with a series of bent and retractile spines. 

 3. TREMATODES : Body flattened or slightly cylindrical, soft, 

 and provided with pores for suction. 4. CESTOIDEA : Body 

 elongated, flattened, soft, of one or many pieces. 5. CISTI- 

 CORUS : Body terminated by or adhering to a vesicle. This 

 arrangement includes besides three isolated genera, which would 

 not admit of being placed under the previous heads. La- 

 treille, in his Families du Regne Animal, disposes the intes- 

 tinal worms chiefly after the methods of Rudolphi and Cuvier ; 

 combining in his sketch of the class the general views of these 

 excellent naturalists. As the method of Latreille is here fol- 

 lowed with one exception, it is not necessary to repeat the 

 characters of the subdivisions. That branch of natural science 

 which treats of Intestinal Worms is generally termed Helniin- 

 thology. 



