THE VOYAGE OF H.M.S. CHALLENGER. 
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Stelechopus numerous parallel muscle bundles (fig. 1, mm.), reaching on both sides from the 
intestine to the integument. The intestine (i.) is more simple in structure, and there is 
no development of lateral diverticula; the entire alimentary canal is a simple tube (i.) 
passing through the body; it is frequently constricted, and at each constriction there is 
often a slight bulging out, but there is not any regularity to be observed in the arrange- 
ment of those bulgings ; only in one individual (fig. 2) there was at the commencement, 
a rudimentary diverticulum divided into three branches. The mouth is sometimes a small 
transverse slit, and sometimes a conspicuous round aperture of T6 mm. diameter 
(fig. 3, m.), situated below the anterior margin of the body. It opens into a muscular 
tube, the pharynx (ph .), which does not, as it appears to do in fig. 1, pass directly into 
the intestine at its commencement, but opens into it some way behind from above, so 
that there is an anterior blind prolongation of the intestine. In none of the specimens 
did this pharynx project out of the mouth. With regard to the terminal part of the 
alimentary tract, I got no certain results ; however, the tube which opens at the end of 
the caudal appendage would seem to be the cloaca, since the intestine appears to be 
continued into it, and I observed a mass of granular crumbling substance, which I believe 
to be feces, projecting from it; also a muscular tube opens into it from above (od.), 
which must represent an oviduct, since there were a number of eggs visible in it. 
If this interpretation be right, then there is exactly the same relation between the 
rectum and the oviduct as in the genus Myzostoma. Mature ova are seen scattered 
through the body as oval or round bodies of '06-T mm diameter, with a nucleus of ’03 mm. 
and a nucleolus of '008 mm. in breadth (fig. 7). There are also to be found at the sides of 
the body, between the intestine and the integument, numerous accumulations of cells, 
which are distinctly different from the eggs by their granular appearance and smaller 
and variable size ; these may serve as male genital cells. Since the specimens were not 
very well preserved, I can say nothing positive about these cells, neither have I succeeded 
in finding the male genital openings. It is possible, therefore, that the male sexual 
products find their way to the exterior by way of the cloaca, and it would be of the very 
greatest importance to clear up this point, which has special bearings upon the affinities 
of the group with the Tardigrada. This is all that I have been able to make out 
concerning the structure of this highly interesting form ; too little, seeing its great 
importance, but sufficient to warrant its separation from the other Myzostomida. 
Host. — Hyocrinus and Bathycrinus, off Crozet Islands, 1600 (Station 147) and 1375 
fathoms, Challenger Expedition. 1 
1 The label on the two preparations of v. Willemoes Snhm is “ Myzostomum from Hyocrinus, 1600 fathoms, off 
Crozet Islands,” but the passage in his sixth letter, which undoubtedly refers to these specimens, says : — “ Ausser diesen 
gewobnlichen Myzostomen gibt es ubrigens auf Crinoiden noch andere allerdings mit diesen verwandte Parasiten, die 
ich im antarktischen Meer bei den Crozet-Inseln auf den aus 1375 Faden heraufgebrachten Gattungen Hyocrinus und 
Bathycrinus fand, Myzostomiden die ich einst daheim in Musse zu bearbeiten hoffe ” ( Zeitschr . /. wiss. Zool., Bd. xxvi. 
p. lxxix.). 
