346 Prof. P. J. Van Beneden on the Tntestinal Worms, 



etoma belongs, are propagated in two ways — by germs in the 

 non-sexual generation, and by eggs in the sexual. These are 

 small and very numerous. The embryo is always covered with 

 cilia (this form is named Proscolex), and for a time lives freely 

 in the water. From this embryo a vermiform creature proceeds 

 that might almost be named a germ-sac (sporocyst) ; it lives 

 parasitically in closed cavities, and is named Scolex by our au- 

 thor. The numerous germs which are developed in this germ- 

 sac, and are provided with a filiform appendage, a tail, again 

 live freely in water. They are the well-known Cercarics — here 

 named Proglottis ; they enclose themselves in a cyst, and, losing 

 their tail, are now changed into Distomata, which again live 

 parasitically, but in cavities of the body that open freely out- 

 wards, as in the respiratory organs or the intestinal canal. 



Of these Trematodes digeneses the following species are here 

 described : Monostoma mutabile, Monostoma verrucosum, Amphi- 

 ^toma subdavatum, Distoma militare, Distoma echinatum, Distoma 

 retusum, Distoma clavigerum, Distoma tereticolle, Distoma filicolle 

 (Monostoma filicolle), Rud., Distoma Okenii, Kolliker, and Ne- 

 matobothrium filarina. Of most of these the difierent forms of 

 embryos, sporoeysts, and cercarise are given. To Distoma militare 

 V. Beneden refers the Cercaria pacifica, which Steenstrup had 

 ^gured in his well-known work on alternating propagation ; the 

 sporoeysts and cercariae are met with in Paludina vivipara, whilst 

 the Distoma-hrm is found in the intestinal canal of Anatidee and 

 other water-birds, and of snipes. The cercaria-iorms of Distoma 

 retusum and D, clavigerum have been confounded under the 

 name of Cercaria armata. Of Distoma filicolle two are com- 

 monly found in one cyst^ on Brama Raji of the Mediterranean 

 Sea ; they are very unequally developed : the one ends in a wide 

 sac, which is bent into a curve, and resembles the body of a 

 larva of the cockchafer ; the other is thin, and was supposed by 

 lludolphi to be an imperfect specimen — the neck without the 

 body of the worm (Synopsis Entozoor. p. 348). Nematobothrium 

 is a new genus, found, like the above-named genus Calceostoma^ 

 by V. Beneden on Scicena Aquila. It is a long, thin, soft worm 

 (about 1 metre long), which, rolled up into a pellet, lives under 

 the skin near the gills. This worm forms as it were the trans- 

 ition to the Cestoids. V. Beneden could not discover any intes- 

 tinal canal, but thinks that it may have been present in some 

 earlier state of existence, before the sexual organs were entirely 

 developed. 



- With the Cestoids or tape-worms, V. Beneden adopts a similar 

 distinction or division as with the Trematodes. According to him, 

 they may be distinguished as Cesto'ides monogencses and Cesto'ides 

 digeneses, Tq the first belongs the genus CaryophylUeus alone 



