684 



The genus Pleurogenes was founded to receive all worms of the 

 general structure of Distomum clavigerum Rud. having marginal 

 genital openings (Loo s s 1896 p. 97). This is the one feature which 

 separates them from groups that are otherwise very similar in organi- 

 zation {Lecithodendrium , Levinseniella etc.), and here at the outset 

 Loxogenes may be distinguished from Pleurogenes on account of its 

 genital opening being situated on the ventral surface, midway be- 

 tween the left coecum and the margin. Brandesia turgida Brandes 

 has been already separated by Stossich (Lo Smemb. d. Brachy- 

 coeliiim 1899) and Prosotocus confiisus and tener Looss have been 

 removed by Looss (Weitere Beiträge 1899) who further suggests 

 that the latter species may have to be placed in a genus of its own. 

 Diphtherostomuin hrusinae Stoss. and DÌ2)h. luteum van Ben. (= D. 

 betencourti Mont.) are also eliminated by Stossich (Note distomolog- 

 iche 1904). There remain Pleurogenes claviger Rud. (type), P. me- 

 dians 01s. and P. gastroporus Luhe. From this it will appear that 

 other characters than the position of the genital opening may suffice 

 to distinguish a new genus even in this small group (subfamily). 

 The long coeca of P. claviger and the position of the testes give to 

 that worm a distinctly different type from the other two and perhaps 

 furnish as good reasons for separating it from the others as in the 

 cases of Prosotocus and Brandesia. I have often throught that the 

 worm Looss figured on p. 100 of the text of »Die Dist. u. Fische 

 u. Frösche 1894« was an individual of a rarer European species 

 (genus?) which perhaps Pagenstecher also saw (Trematodenlarven 

 etc. 1857 Taf. IV. fig. VIII). With these eliminations the figures of 

 P. claviger present a pretty imiform j)icture (Those of Schwarze, 

 von Lin stow, and the Leuckart charts have the testes in the 

 extreme end, that of Molin has the vittellaria far back along the 

 sides etc.) 



The classification of those members of the group that are parasitic 

 in amphibia will depend upon the rank given to (1) the position of 

 the genital opening, (2) the position of the testes, (3) the position of 

 the ovary, (4) the length of the coeca. Giving primary importance 

 to (1) separates Loxogenes from both Pleurogenes and Brandesia, 

 while giving prominence to (2) will bring it into relation with Pleu- 

 rogenes but leave it separate from Brandesia etc. I have classified 

 them in many ways, and I cannot convince myself that there is 

 much to be gained by any one way, so I shall content myself by 

 recounting the main differences from Pleurogenes and Bì^andesia. 



The habitat is different, for Loxogenes occurs in thick- walled cysts 

 in the liver or pylorus whereas Pleurogenes occurs free in the cavity 



