134 COMPARATIVE ANATOMY CHAP. 



Tribe 1. Alloioccela. 



Intestine sharply separated from the parenchyma, often with short lateral sacs. 

 Numerous small testes. Female germ glands either 2 ovaries or 2 germ -vitellaria, 

 or separate germaria and vitellaria. Monotus, Plagiostoina, Vorticcros. 



Tribe 2. Rhabdoccela. 



Intestine sharply separated from the parenchyma, without lateral diverticula. 

 In the parenchyma there occur spaces, generally of considerable size, filled with 

 fluid, which form a sort of ccelome. 2 large testes. Female germ glands either 



1 or 2 ovaries, or 1 or 2 germaria and vitellaria, or 2 germ - vitellaria. Vortex, 

 Graffilla (parasitic), Macrorhynchus, Mesostoma, Prorhynchus, Microstoma and Steno- 

 stoma (in these two genera the sexes are separate), Macrostoma. 



Tribe 3. Accela. 



Without distinct intestinal canal ; with digesting parenchyma. Without excre- 

 tory organs ; with numerous very small testes, and 2 ovaries. Nadina, ConriiJiitn. 



CLASS II. Trematoda. 



Parasitic unsegmented Platodes, without covering of cilia, mostly with forked 

 intestine. Mouth and pharynx at the anterior end of the body. 2 testes, 1 ger- 

 marium, and 2 vitellaria branched or divided into numerous lobes. 



Order I. Ectoparasitica (monogenetic). 



With at least 3 suckers. Development direct, without alternation of genera- 

 tions, or heterogeny ; life-history simple. Tristomum, Diplozoon (two young, not 

 yet sexually mature animals early fuse in the shape of a cross, and only become 

 sexually mature in this condition) Polystomum, Gyrodactylus. 



Order II. Endoparasitica (digenetic). 



With at the most 2 suckers. Life-history with heterogeny. Distoma licpaticum 

 (life-history, p. 169, Fig. 119), D. lanccolatum, both in the bile ducts of the sheep. 

 Distoma isostomum, Gyncecophorus hcematobiits, in the blood in the portal veins 

 of man (in Africa), sexually separate ; the male with a channel on the ventral side 

 for the reception of the female. Amphistoma, Monostomum. The sporocysts and 

 redire usually live in water snails ; the sexual generation mostly in the intestines of 

 vertebrates. 



CLASS III. Cestoda (Tapeworm). 



Endoparasitic Platodes without cilia and without intestine, with numerous testes, 



2 germaria, and 1 or 2 vitellaria broken up into lobes. With organs of adhesion only 

 at the front end of the body. 



Order I. Monozoa. 

 Unsegmented individuals. Amphilina, Caryoj^hyllceus, Archigctes. 



Order II. Polyzoa. 



Cestode stocks arising by strobilatiou : segmented tapeworms. With scolex and 

 chain of proglottides. Pkyllobothrium, Tetrarhynclius, Ligula (very indistinctly seg- 

 mented). Botlirioccplialus latus; broad tapeworm (Fig. 117, O, p. 164) in human 

 intestine. Over 3000 proglottides. With 2 pit-like suckers in the head. Genital 

 apertures on the flat surfaces. Larva ciliated in water. Scolex -like young form 

 in flesh of the Pike, of the Burbot, and perhaps of other fish. Schistocephalus. 

 Tricenophorus. Tcenia; with 4 suckers. T. Saginatct (mediocandlata) (Fig. 117, A., 



