864 DR. F. E. BEDDARD ON 
described by himself, occurring at some distance from the open- 
ing into the receptaculum. It here becomes much narrower. 
Nothing of the kind oceurs in Rhabdometra cylindrica, except, 
perhaps, just at the orifice ; and, moreover, the coating of gland- 
cells extends over the entire vagina, up to the receptaculum. 
The latter is large and spherical to rather oval in form; it lies 
obliquely to the longitudinal axis of the body towards the pore 
side. 
§ The Paruterine Organ. 
This structure is of such importance in the group of tapeworms 
of which the present species is a member, that it needs a detailed 
treatment for comparative purposes. In the living worm the 
paruterine organ is exceedingly conspicuous as a rod-like body 
at the anterior end of the proglottid, often of a brilliant white, 
thus contrasting with the more pellucid tissues of the outer layers 
of the worm. This aspect led me at first to regard the paruterine 
organ as the uterus crammed with eggs, which might be expected 
to show a bright white owing to the innumerable separate and 
minute embryos. In the proglottids the increasing length of 
the paruterine organ could readily be observed owing to its ex- 
treme conspicuousness. It was so distinct from the rest of 
the proglottid in its neighbourhood, that each paruterine organ 
suggested a conical peg attaching two consecutive segments. In 
the living worms the paruterine organ is a perfectly rod-like 
structure, without any obvious twist of any kind. It was seen to 
diminish slightly in width at its terminal end, and was never 
seen to extend to the posterior end, though the organ appeared to 
commence at the very beginning of the proglottid. The whole 
appearance of the organ as seen with a lens, suggests that it is 
produced by a growth from before backwards, and not vice versa. 
In alcohol-preseryed examples the paruterine organ is no longer 
visible in the intact worm, nor is it in specimens examined 
whole after clearing but without staining. This seems to suggest 
that the bright white appearance of the paruterine organ in 
the living worm is caused by air-spaces in the spongy tissue of 
which the organ is composed. But it must be admitted that this 
of itself is difficult to understand. Still, the organ certainly has 
the appearance during life of being composed of a fine froth. 
I have examined the organ in the preserved worms by means of 
transverse and longitudinal sections. I have already spoken of 
the organ when fully developed as being rod-like, or perhaps 
rather style-like, as it diminishes to one end. But in trans- 
verse sections it is seen that the paruterine organ is only 
rod-like, and thus circular in section, in the fully mature pro- 
glottids. These proglottids are themselves tubular and oval, 
or even quite circular in transverse section. In more anterior 
segments the form of the proglottid is more flattened, and the 
paruterine organ shares in this alteration of form. In such 
proglottids the organ is more flattened and tends to have the 
