56 CONTRIBUTIONS TO AMERICAN HELMINTHOLOGY. 
being provided on each side, at any rate in the trunk, with short, 
sometimes branched, diverticula (Fig. 2), which, however, project 
much less in the most extended condition of the animal. This 
character seems to be shared by D. dimorphum,* and although pre- 
sent in many Polystomer (Epibdella, Diplozoon, Onchocotyle, &c.), 
is by no means common in Distomez.° 
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 conyo- 
luted lateral stems, which run along the sides to the neck. During 
life I observed that the granules contained in these also circulated 
through the vacuolated 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- 
val between these at the hinder end of the body. The testes (¢) 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 inclined to believe a canal (vagina?) passes upwards 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- 
ture 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 Vorticella. This is followed by a rapid retrac- 
4 Diesing’s fig., loc. cit. 
5 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. IIL., p. 5, 
