6 4 



THE TREMATODA 



The adults live in Vertebrata, and nearly always in tlie enteron or its 

 outgrowths ; the intermediate host is usually a mollusc. 



FAMILY 1. AMPHISTOMIDAE. Body more or less cylindrical ; oral 





--a 



7 



FIG. X. Some Malacocotyleans. 



Letters common to all the figures, except Fig. 8. a, mouth and oral sucker ; b, genital 

 pore ; c, posterior ventral sucker. 



1. Amphistomum conicum, Zed., from the paunch of the cow; ventral view (after Laurer). 

 The genital pore is at the apex of a small papilla surrounded by a shallow groove (cf. Fig. A). 



2. Homologaster paloniae, Poir., from the caecum of Palonia (Bos) frontalis ; ventral view 

 (after Poirier). p, the adhesive papillae covering the ventral surface. 



3. Gastrothylax cobboldii, Poir., from the stomach of Palonia; lateral view (after Poirier). 

 The furrow surrounding the genital papilla has become deepened to form a sac (cf. Fig. B), the 

 entrance to which is labelled d. Figs. A and B are immediately below 2 and 4 respectively. 



4. Ogmogaster plicata, Crepl., from the caecum of Balaennptera sp. ; ventral surface (after 

 Jagerskiold). r, the longitudinal ridges constituting a secondary adhesive organ. 



5. Notocotyle serialis, Dies., from the colon of Anas penelope ; dorsal surface (after Diesing). 

 s, the dorsal suckers in three rows. 



6. Didymozoon thynni, Tschbg. (= Monostoimim bipartitum, Wedl.), from a cyst on the 

 gills of Thynnus vulgaris (after Wagener). The two individuals are closely wrapped round one 

 another, their "heads" projecting freely. 



7. Anterior sucker of Gasterostomum fimbriatum, v. Sieb., from the stomach of the pike 

 (after Wagener). ee', the tentacle-like processes from its margin. 



8. Gasterostomum armatum, Mol., from the intestine of Cottus scorpio ; ventral view (partly 

 after Molin, partly after Levinsen). b, genital pore ; e, anterior sucker ; /, vitellarium ; g, 

 simple sac-like intestine ; h, the left vitelline duct, which unites with its fellow, and opens 

 by a median duct into the germ duct ; i, uterus ; j, germarium ; k, mouth, which has a position 

 unique amongst the Trematoda, nearly in the middle of the ventral surface ; I, the right testis ; 

 m, seminal vesicle ; n, cirrns sac ; o, cirrus or penis ; u, excretory pore. 



9. The smaller of the two individuals of Didymozoon, probably the male. (After Wagener.) 



10. Monostominn mutabile, Zed., from the sub-orbital sinus and body cavity of various 

 aquatic birds. (After P. J. van Beneden.) , excretory pore. 



11. Opisthotrema cochleare, Lkt., from the tympanic cavity and Eustachian tube of Halicore ; 

 ventral view (modified from Fischer). The genital pore (b) is posteriorly placed. 



