56 CONTRIBUTIONS TO AMERICAN HELMINTHOLOGY. 



being provided on each side, at any rate in the trunk, with short, 

 sometimes branched, diverticuha (Fig. 2), which, however, project 

 much less in the most extended condition of the animal. This 

 character seems to be shared by D. dimorphnm,- and although pre- 

 sent in many Polystomese (Epibdella, Diplozoon, Onchocotyle, &c.), 

 is by no means common in Distomese.^ 



The ventral sucker is situated 0.8 mm. behind the anterior, and is 

 0.8 mm. in diameter. Its cavity is deep and gaping during life ; 

 frequently its orifice is circular from strong contraction of the radial 

 fibres, usually shield-shaped or triangular. 



The excretory system has a large caudal pore, and two much convo- 

 luted lateral stems, which run along tLe sides to the neck. During 

 life I observed that the granules contained in these also circulated 

 through the vacxiolated parenchyma of the body, although they did 

 not seem to enter the plexus of fine canals which could be seen 

 immediately under the outermost investment. The parenchyma 

 reminded me of that which I have myself observed, and which has 

 been described by Fol and others, in the foot of embryonic Gastro- 

 pods. This connection between water-vascular system and paren- 

 chyma spaces has been insisted on by Sedgwick Minot.^ 



I have not been able to follow satisfactorily all of the genital 

 organs. The vitellogens (see Fig. 1) are in the form of racemose 

 glands grouped round the intestinal coeca, and occupying the inter- 

 nal between these at the hinder end of the body. The testes [t) are 

 two in number, and between them are the ovary, first convolutions 

 of the oviduct, and a retort-shaped receptaculum seminis, from which 

 I am incliued to believe a canal (vagina*?) passes upwai'ds towards 

 the back, although I have failed to detect this in my preserved 

 specimens. Towards the right side of the anterior testis is a struc- 

 tui*e whose function I have not been able to determine. It is pos- 

 sibly the thickened end of the oviduct at its junction with the uterus ; 

 at any rate the thickened tube projects into the bottom of the thin 

 walled uterus, and is subject to a regular and slow evagination of 

 the anterior part of its inner surface, recalling the gradual eversion 

 of the peristome in a Yorticella. This is followed by a rapid retrac- 



*Diesing's flg., loc. cit. 



6 Schmarda, Zoologie, attributes this character to D. cygnoides and clavigerum of the Frog ; 

 Pagenstecher's figures (Trematodenlarven und Trematoden) do not corroborate this. 

 6 On Distomum crassicolle. Mem. Bost. Soc. N. H., Vol. III., p. 5. 



