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the sperm-ropes of two species of Tubifex—T. rivulorum, a 
worm abundant in nearly every muddy stream or river, and . 
T. umbellifer, a remarkable form, living with the latter and 
Limnodrilus Udekemianus, in the Thames below London (see 
‘ Annals and Magazine of Natural History,’ February, 1871). 
The sperm-ropesof Tubifex rivulorum I have found in the 
copulatory pouches both in summer and winter, but especially 
abundant and well-formed in the winter. They have a worm- 
like figure, with a curious conical head, and average from 
aisth to 4th of an inch in length, and from =1,th to =',th 
of an inch in breadth, the narrowest part being that im- 
mediately succeeding the conical head, which has a breadth 
of about +,%,,ths of an inch (Pl. X, fig. 1). ° 
The general form of the sperm-rope is due to its being 
moulded in the long neck of the copulatory pouch. This is 
plainly seen from the manner in which the conical head cor- 
responds with the shape of the orifice of the pouch (fig. 18). . 
The sperm-rope may sometimes be seen lying in this position, 
in course of being moulded. The sperm-rope of JZ. wmbel- 
lifer does not present the conical head which we find in 7. 
rivulorum, and in accordance with this is the absence of the 
reduplication of the wall of the copulatory pouch at its orifice ; 
the mouth is simple, and accordingly gives rise to a simple 
tapering extremity in the sperm-rope. 
Not all the sperm-ropes, however, which are to be met with 
in the reservoirs of 7. rivulorwm have the conical head ; some 
have been moulded lower down in the neck, and, conse- 
quently, exhibit a single blunt extremity, as fig. 9; others, 
again, from an insufficiency of the plastic material, are quite 
short, and consist of nothing but the conical head (fig. 8). 
All gradations are to be met with, parts of the conical heads 
short and long, according to the amount of plastic material 
introduced into the moulding reservoir-neck, and according 
to the part of the neck in which the moulding has taken 
effect. 
It appears that the material of which the sperm-ropes are 
formed, namely, spermatozoa and a cementing matrix, must 
be introduced in a viscid form from the male efferent duct, 
through the penis of one worm into the copulatory reservoir 
of another, and in the neck of that reservoir a “setting” 
occurs ; for the sperm-ropes, when fully formed, are very firm 
and compact bodies, of high light-breaking power. The wall 
of the copulatory pouch is glandular, and undoubtedly fur- 
nishes a secretion which occupies part of its cavity, and 
in all probability also assists as a cementing material in 
the formation of the sperm-ropes. But the fact that the 
