No. 2.] A NEW MARINE TRICLAD. 183 
rami. The center of each mass is usually, although by no 
means always, filled with a more opaque substance (sp) immedi- 
ately surrounding which there is a pale halo (ws). In carefully 
stained specimens each uterus is seen to possess an inde- 
pendent opening on the ventral surface (oz). The relations of 
these openings to the longitudinal nerve-cords are seen in 
Fig. 3 07. The apertures occupy the posterior inner edges of 
uteri. In preserved specimens the apertures themselves are 
very small, but there is a pale enucleate halo surrounding each, 
so that they may be readily found. 
In sagittal section (Fig. 8) the uterus is seen to take up 
nearly the entire thickness of the body. Externally its wall is 
sharply defined, but internally it is very ragged, at least in 
certain stages of its physiological activity, the single layer of 
cells composing it being frayed out at their inner ends. The 
nuclei of these cells (7) are few in number and stain very 
faintly. The mass in the center (sf), which shows as an 
opaque body in specimens studied zx soto, is a compacted ball 
of spermatozoa, and the pale halo surrounding it (in the section 
Fig. 8 represented by two fragments only, ws) is a glairy coag- 
ulum which usually envelops the mass of spermatozoa, and 
which I take to be the secretion of the cells of the uterine 
wall. The opening of the uterus is shown in section at ow. 
The walls of the delicate lumen, which appear to consist of a 
chitinous substance, are very thick and concentrically striated. 
A small nodule (v/), perhaps a kind of valve, seems to occlude 
the lumen. Then follows a more dilated cavity communicating 
with the cavity of the uterus proper. 
In &. candida the conditions are similar, but more easily 
studied on account of the much greater size of this Triclad. 
The duct runs to the exterior from the anterior instead of the 
posterior inner surface of the uterine sac. In section (Fig. 9) 
the epithelial character of the wall is. easily studied. It agrees 
in all essential respects with the uterine epithelium of the 
fresh-water forms. The duct has a very distinct lumen (oz) 
which is ciliated up to the valve (v/). There is also a 
slightly dilated portion connecting the duct with the uterine 
cavity proper as in Syncelidium. Contrary to v. Graff’s 
