316 PLATYHELMIXTHES. 



elongated and flattened body, which is provided with a foot-like ventral surface. 

 Geoplana lapidicola Stimps., IthyncJiodesmus terrestris Gm. {Fasciola terrestri*, 

 0. Fr. Miiller), Europe. Geodesmus biluieatus, Metschn., with thread cells in 

 the integument, found in potter's earth. 



2. Digonopora. Dendrocoda with double sexual opening. Almost 

 all are marine. The proboscis is often folded and lies within a 

 special pouch. When protruded, it spreads out like a lobe. 



Fam. Stylochidae. The body is flat and rather thick, and is provided with 

 two short tentacles on the head. There are usually numerous eyes on the 

 tentacles or on the head. The genital openings are posterior. Stylockus macu- 

 latus Quatr. 



Fam. Leptoplanidae. Body flat and broad, usually very delicate. Cephalic 

 region not distinct, without tentacles. The eyes are more or less numerous. 

 The mouth is usually placed in front of the middle of the body. The genital 

 openings lie behind it. Leptoplana tremellaris O, Fr. Mull., Mediterranean. 



Fain. Euryleptidae. Body broad, and either smooth or furnished with 

 papillae. There arc two tentacle-like lobes on the anterior region of the head. 

 The mouth is placed in front of the middle of the body. Numerous eyes are 

 disposed near the anterior margin. Marine. Thysanozoon Diesingii Gr. 

 Mediterranean. Eurylepta aurlculata 0. Fr. Mailer, North Sea. 



Order 2. TREMATODA.* [ 



Parasitic Platyhelminthes with unsegmented, usually leaf-sliaped, 

 rarely cylindrical body. TJiey possess a mouth and ventrally placed 

 organ for attachment : the intestine is forked and ivithout an anus. 



The Trematodes are with great probability to be derived from 

 the Turbellaria, with which group, both in form and organization, 

 they show a close relationship. In connection with their parasitic 

 mode of life they develop special organs for adhering, such as 

 suckers and hooks. Cilia are present only in larval life. 



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

 usually in the middle of a small sucker (fig. 253). It leads into 

 a muscular pharynx with a more or less elongated oesophagus, which 

 is prolonged into a forked intestine ending blindly. 



Moseley, " Notes on the Structure of Several Forms of Land Planarians," etc. 

 Jovrnal of jllicr. Science, vol. xvii. 



* A. v. Nordmann. " Mikrographische Beitrage zur Kcnntniss der wirbelloscn 

 Thiere," Berlin, 1832. G. G. Cams, " Beobachtung iibcr Leucochloridium 

 paradoxum. etc.," Nov. Act., vol. xvii., 18:55. Wagener, " Ueber Gyrodactylus 

 elegans." Mullens Archiv., I860. Van Beneden, " Memoire sur les vers intes- 

 tinaux," Paris, 1801. E. Zellcr, " Untcrsuchungen tiber die Entwickelung und 

 den Bau von Polystoma integerrimum, Zeitsclir. f. n-ixs. Zool., vol. xxii., 1872. 

 E. Zeller, "Untcrsuchungen iibcr die Entwickelung .von Diplozoum paradox- 

 um," Hid., vol. xxiii., 1873. E. Zeller, " Ueber Leucochloridium paradoxum 

 und die wcitere Entwickelung seiner Distomumbrut," Hid.. Tom XXIV. 

 E. Zeller, " Weitercr Beitragzur Kenntniss der Poly stomeen," Hid., xxvii., 187G. 

 Compare also the works of G. Wagener and De Filippi. 



