BY S. J. JOHNSTON. 285 



genital opening, cirrus, and cirrus-sac would occupy similar 

 positions; the configuration and extension of the yolk-glands and 

 yolk-ducts would be practically the same. Such an alteration in 

 the shape of Hapalotrema, with the simple alteration of the 

 position of the internal organs, an obvious consequence of this 

 alteration in shape, would produce a worm strikingly similar to 

 Moreauia. Other similarities would be found in the form of the 

 suckers, and in their position, not only in regard to one another, 

 but also in regard to the other organs of the body; in the thin 

 character of the integument and the absence of spines, complete 

 in Moreauia, and almost complete in Hapalotrema. Important 

 differences are the absence of the pharynx in the latter, and the 

 very much more strongly developed cirrus-sac and the conspicuous 

 pars prostatica in the former. The systematic position of Hapa- 

 lotrema has been variously estimated by different writers on this 

 group of animals. Looss(4) considers it closely related to Bil- 

 harzia (Schistosomum), mainly on the grounds of a similarity of 

 certain external features (integument and suckers), the conforma- 

 tion of the alimentary tract, and the miracidia. PrattdD places 

 it with the Clinostominae, while Odhner(8) places it, along with 

 Liolope, in a subfamily Liolopinse. The last arrangement, I 

 consider the most satisfactory. Moreauia shows so many dis- 

 tinctive features, that it can hardly be placed in the Liolopinie, 

 but must be considered the representative of a new subfamily, 

 MoREAUiiNiE, which has close affinities with the Liolopinae. The 

 chief differences between the two groups, besides those concerned 

 with the unique shape of Moreauia and the consequent rearrange- 

 ment of the relative positions of some of the organs, are the 

 presence of a very marked pars prostatica in Moreauia, and a 

 very strong cirrus-sac, within which the vesicula seminalis is 

 also included (it lies quite outside the relatively small cirrus-sac 

 in Hapalotrema) [5, Fig. 7 3]. 



LITERATURE REFERRED TO. 



I.Braun, 1900. "Die Arten der Gattung Clinostomum Leidy." Zool. 



Jahrb. Syst., xiv., pp. 1-48. 

 2.C0HN, 1902. *' Zwei neue Distomen." In Ceutralbl. f. Bakt., Bd.32. 



