2 C. S. MINOT ON DISTOMUM 



the end of the anterior third of the body. The posterior two-thirds are taken up mainly 

 by the convolutions of the uterus, Ut, which in all the specimens I have examined was 

 filled with an enormous number of eggs. The yolk glands of authors, or the egg-food- 

 stocks, F, as they may be more appropriately named, lie on each side of the body, forming 

 two masses, which when seen from above have a triangular outline. They are restricted to 

 the first third of the body. The mouth occupies the middle of the front sucker, 31. The 

 digestive canal begins with a very short tube, above which lies the central nervous system, 

 JV, and which leads to the muscular pharynx, Ph. The canal continues beyond this, simple 

 and of small diameter, until it gets about half way to the ventral sucker, where it divides, 

 sending a simple sac-like branch, D, obliquely backwards and outwards on each side. These 

 branches do not extend beyond the level of the front edge of the ventral sucker and end 

 blindly. The digestive tract is therefore remarkably small and simple in proportion to the 

 size of the animal. Tbe ovary, Ov., is a rounded body lying asymmetrically upon the right 

 hand of the ventral sucker, in front of which there is a small depression, the sexual antrum, 

 ( Geschlechtsvorraum), in the right of which the sheath of the penis, Pe., opens, while the 

 uterus, Ut, opens on the left. The penis runs backward over the sucker, and behind the 

 point where it is attached to its sheath, it enlarges to form the penis bulb, which corre- 

 sponds to the Cirrhasbeiitel of the Cestods. 1 The testes, two in number, are of unequal 

 size and asymmetrically placed. That on the left, Te., is the smaller, and lies the further 

 forward, being quite near the ventral sucker, while the slightly larger right-hand testis, Te.', 

 is placed further back. They are both nearly spherical. The spermiduct, Sp. d., from each 

 is very fine, and runs towards the penis bulb, into which it undoubtedly opens, though I 

 have not been able to discover the exact communication. The uterus, Ut, extends back- 

 ward from its external opening, and, passing beyond the penis-bulb, then enlarges and 

 forms the unusually complicated convolutions which, as before mentioned, fill up the pos- 

 terior two-thirds of the body, and which I found it impossible to follow. It ends, however, 

 in the shell gland (Schalendruse), which lies just behind the penis, but is not represented 

 in fig. 1. The oviduct and the ducts of the egg-foodstocks also communicate with the 

 shell gland, from which a fine tube also runs upwards to open on the back. The main 

 stem, W.v., of the water vascular system extends from the hind end of the animal straight 

 forward half the length of the body. Its diameter gradually diminishes as it runs forwards. 

 It is hoped that this brief account of the general topography of the organs will serve to 

 characterize the species, and render the following details intelligible. 



In all my sections I find the outside limit of the body to be a membrane, fig. 9, B.M., 

 of nearly even thickness, but without any distinct structure, unless a faint striation indicat- 

 ing a fibrillar composition be regarded, as such. It is armed with a number of very minute 

 spines, which lie close together and are restricted to the anterior part of the back. This 

 membrane is the cuticula of authors. I cannot accept that designation, because I consider 

 it to represent a basement membrane. I have in my two previous papers already suggested 

 this homology. I have accordingly attempted to find epidermal cells lying exteriorly to 

 the membrane in question, but hitherto without success. I must, however, still maintain 



1 Leuckart. Die mensclilichen Parasiten. Bd. i, p. 178-179. 



