116 



ENTOZOA. 



the immature states of the higher orders of 

 SlerrlmmUia. 



OUDO II. CESTOIDEA, (XEOTOS, cingulum, 

 nJo;, forma.) 



Verities taniieformes, Bundwurnicr, 



Tape-worms. 



Char. Body elongated, flattened, soft, 

 continuous, or articulated. Head either 

 simply labiate, or provided with pits 

 (boi/iria) or suctorious orifices (oscula 

 ntctoria) either two or four in number, 

 and sometimes with four retractile un- 

 armed or uncinated tentacles. Andro- 

 gynous generative organs. 

 Obs. In this order Rudolphi includes the 

 inarticulated Liguhe, with simple heads un- 

 provided with bothria or suckers; a conjunc- 

 tion which detracts from the natural character 

 of the group. Cuvier separates the Ligula 

 from the Tanitse, and they form exclusively his 

 Order Cestoidea ; it must be observed, however, 

 that the passage from the one to the other is 

 rendered very gradual by the traces of bothria, 

 and of generative organs which appear in the 

 higher organized Ligula: found in the intestines 

 of Birds ; and respecting which Rudolphi 

 hazards the theory that they are the more simple 

 Ligula: of Fishes, developed into a higher grade 

 of structure by the warmth and abundant nutri- 

 ment which they meet with in the intestines of 

 Birds which have swallowed the Fishes infested 

 by them. 



OBDO III. THEMATODA, (r^>)ft, foramen, 

 TJiaTo>Ji)C foramiiuufus.) 



Verntei sitctorii, Satigwitrmer, Fltthe- 



wornts. 



C/iar. Bcdy soft, rounded, or flattened. 

 Head indistinct, with a suctorious fo- 

 ramen ; generally one or more suctorious 

 cavities for adhesion in different parts of 

 the body. Organs of both sexes in each 

 individual. 



Obs. This very natural order includes, in the 

 system of Cuvier, many species which do not 

 infest other animals, but are found only in 

 fresh waters ; these non-parasitic species form 

 the greater part of the genus P/anaria of Muller, 

 (Jig. 80.) Hudolphi, who seems to have sup- 

 posed the PUmerue to be of a more simple 

 organization than they truly possess, approxi- 

 mates them to the Ligula: or inarticulated Ces- 

 toidea. Other naturalists, unwilling to asso- 

 ciate the Plaiiariie with the Entozoa, have 

 placed them in the Class Anellida, but the 

 absence of a ganglionic abdominal nervous 

 chord, of a floating intestine, and of an anus, 

 renders such an association very arbitrary. 

 OKDO IV. ACANTHOCEPIIALA, (axat&a, 

 tphia, x.t<fa,\n, ca/jut.) 



Venues mieinati, Hacken-wuiiner, 



Hooked-worms. 



Char. Body elongated, round, sub-elas- 

 tic. Head with a retractile proboscis 

 armed with recurved spines, (Jig. 74.) 

 Sej'uiii Organs appropriated to distinct 

 individuals, male and female. 

 Obs. This natural group includes the most 

 noxious of the internal parasites ; fortunately 

 no species is known to infest the human body. 



They abound in the lower animals, and present 

 great diversity of form, some being cylindrical 

 and others sacciform. 



OiiDoV. NEMATOIDEA, (tri^it,Jilum, tiJof, 

 forma.) 



Vermes teretes, Rund-w'iirmcr. Round- 

 worms. 



Char. Body elongated, rounded, elastic. 

 Month variously organized according to 

 the genera. A true intestinal canal 

 terminating by a distinct anus. Sejces 

 distinct. 



Obs. The internal character which Rudolphi 

 has introduced in his definition of this Order,* 

 viz. that derived from the structure of the ali- 

 mentary canal, its free course through the body, 

 and its termination by a distinct anus at the 

 extremity opposite the mouth, is one of much 

 greater value than any of the external modifica- 

 tions of the body which characterize the four 

 preceding orders. It is, in fact, a trait of or- 

 ganization which is accompanied by corre- 

 sponding modifications of other important 

 parts, more especially the nervous system. 



The Entozoa which manifest this higher type 

 of structure form in the system of Cuvier a 

 group equivalent to that which is constituted 

 by the four other orders combined. The En- 

 tozoa composing the first four orders above 

 characterized have no distinct abdominal cavity 

 or intestine, but the digestive function is carried 

 on in canals without an anal outlet excavated 

 in the parenchymatous substance of the body, 

 and Cuvier accordingly denominates them the 

 Vers Iniestinuux parenthymateur. The Ne- 

 mutoidea, with which Cuvier rightly associates 

 the genus Pentastoma of Rudolphi, and also 

 (but less naturally) the Vcrs rigidules of La- 

 rnarck, or Epizoa, he denominates ' Vers intes- 

 tinuux cavitaires.' 



With respect to the Epizoa, or the external 

 Lerna/an parasites of Fishes, although they 

 agree with the Nematoidea and all inferior 

 Entozoa in the absence of distinct respiratory 

 organs, yet the ciliated natatory members which 

 they possess in the young state, and the exter- 

 nal ovarian appendages of the adult, are cha- 

 racters which raise them above the Kntozoa as 

 a distinct and higher class of animals, having 

 intimate relations with the soft-skinned Sipho- 

 nostomous Crustaceans. 



Limiting, then, the Cavitary Entozoa to the 

 Nematoidea of Rudolphi, and the Genera Lin- 

 gnatulu, Pentastoma, Porocephulus, and Syn- 

 (sanius, which, under the habit of Cestoid or 

 Tremalode Worms, mask a higher grade of 

 organization, we pro|x>se to regard them as a 

 group equivalent to the Steretmintha, and to 

 retain for them the name of Catlelmintha. 



The class of Entozoa thus constituted em- 

 braces already the types of three different 

 orders, of which one is formed by the Nema- 

 toidea of Rudolphi, a second has been esta- 

 blished by Diesing for the genus Pentusttnua 

 and its congeneric forms, under the name of 



* " Corpus teres clasticum, tractus intestinal!* 

 bine ore, iHinc ano tenninatus. Alia individua 

 mascula, alia feminea." Synops, Entox. p. 3. 



