TREMATODA. 223 



COTYLEA. 



With central or sub-central ventral sucker always placed behind the openings 

 of the body. Mouth in middle of body, or in front of it. Copulating apparatus 

 (except Anonymus) in the anterior half of the body. Without tentacles, or with 

 marginal tentacles. . 



Fam. 1. Anonymidae. Body broad, oval, without tentacles. Numerous 

 penes in two lateral rows. Single female opening between mouth and sucker. 

 Eyes in brain area and on whole edge of body. Anonymus Lang. 



Fam. 2. Pseudoceridae. Body oval or elliptical, with fold-like marginal 

 tentacles. Mouth in middle of anterior half of body. Eyes on brain areas, and 

 on the tentacles. Thysanozoon Grube, with dorsal villi and double penis. 

 Pseudoceros Lang, and Yungia Lang, without villi. In Yungia the gut diverti- 

 cula open by numerous pores on the dorsal surface of the body. 



Fam. 3. Euryleptidae. Body oval or elliptical, with or without pointed 

 frontal tentacles. Mouth near the front end of the body. Pharynx tubular. 

 Eyes in the brain area and on the tentacles (or at the two sides of front edge 

 of body). Prostheceraeus Schmarda, Brit, coast ; Cydoporus Lang, gut branches 

 open along the whole of the edge of the body, C. papillosus Lang, Plymouth, 

 Port Erin; Eurylepta Ehrb. ; Eu. cornuta 0. F. M., Brit, coast. Oligodadus 

 Lang, Brit, coast ; Stylostomum Lang, Brit, coast ; Aceros Lang. 



Fam. 4. Prosthiostomidae. Body elongated, without tentacles. Mouth 

 immediately behind brain. Pharynx long and tubular. Prosthiostomum 

 Quatrefages. 



Class II. TBEMATODA.* 



Parasitic Platyhelminthes with unsegmented, usually flattened, 

 rarely cylindrical, body. They possess a mouth and ventr ally-placed 

 organ for attachment. The intestine is forked and without an 

 anus. 



The Trematodes, in the main features of their organisation, are 

 most nearly related to the Turbellaria. They differ from them in 

 their parasitic habit, and in the absence in the adult of a ciliated 

 ectoderm, though the Temnocephalidae, in possessing a partially 

 ciliated ectoderm and in other respects, are intermediate between 

 the two classes. In connection with their parasitic habit they 

 possess special organs for adhering, such as suckers and hooks, 

 which are stronger and better developed in those which are external 

 parasites than in those which infest the internal organs of animals. 



The mouth is invariably placed at the anterior end of the animal, 

 usually in the middle of a small sucker. It usually leads into a 



* M. Braun, "Trematoda" in Bronn's Klassen u. Ordnungen, Bd. iv., 

 1887-93. A. v. Nordmann, " Mikrographische Beitrdge z. Kenntniss der wir- 

 bellosen Thiere, Berlin, 1832. P. J. v. Beneden and Hesse, Mem. de VAcad. 

 Roy. Belgique, 34, 1864, p. 60. P. J. v. Beneden, Mem. s. Us Vers intestinaux, 

 Paris, 1858-61. v. Linstow, Compendium der Helminthologie, Hanover, 1878. 

 A. P. Thomas, "The Life-History of the Liver-Fluke," Q. J. M. S., 23, liiSS, 

 p. 99. R. Leuckart, "Die Parasiten des Menschen,"Ed. 2, Leipzig, 1879-1894. 

 S. Goto, " Ectopar. Trematodes of Japan, " Journ. Coll. Sci. Imp. Univ. Japan, 8. 



