186 
common salt served to bring them into action when they were 
previously quiescent. 
Sperm-ropes of Tubifex umbellifer—The Sperm-ropes of 
this species, the characteristic setee of which are drawn in 
figs. 16 and 17, are somewhat smaller and of a more elegant 
and tapering form than those of 7. rivulorum. In this in- 
teresting worm—recorded as yet only from the neighbourhood 
of Lake Onega and the Thames—the penis is not preceded 
by a short pyriform glandular enlargement of the vas deferens, 
on to which the-cement-gland is grafted, as in 7. rivulorum, 
but a long tortuous canal, resembling the preceding portion 
of the vas, comes between the penis and the enlargement 
on to which the cement-gland is grafted. This may possibly 
have some connection with the difference in the form of 
spermatophor. The chief difference is in the absence of 
the conical head, which is due to the fact that the neck of 
the copulatory sac in 7. wmbellifer is of a different shape to 
that of 7. rivulorum, and consequently moulds the mixture of 
cement and spermatozoa to another form. This form is seen 
in fig. 14. Both extremities are acute and tapering, but that 
which corresponds to the “head” of 7. rivulorum’s sperm- 
rope is broadened out for some length. This general form 
—but more blunt and rounded than here seen—occurs in 
Limnodrilus and Clitellio (see Claparéde’s figures of Pachy- 
dermon from Clitellio, ‘Recherches sur les Oligochétes’). The 
same constituent parts are noticeable, as in 7" rivulorum, 
but I have not seen sperm-ropes of so compact and dense an 
appearance in 7. umbellifer as in the former species. The 
fringe of vibratile filaments is always deeper and more 
obvious than in J. rivulorum. The axial canal widens out 
toa correspondingly large cavity in the broad anterior ex- 
tremity of this spermatophor, and there are granular or 
sometimes broken-down cellular contents in it. 
Three of these sperm-ropes extruded from their containing 
copulatory pouch into a two per cent. solution of salt, exlibited 
very graceful movements of a definite character. The whole 
body, assuming a double curve of a sigmoid character, moved 
with great rapidity, in such a way as to describe a figure of 
eight passing and repassing on the same track, or very nearly 
the same. Fig. 15 is intended to represent one of these bodies 
in motion ; all three presented the same graceful sigmoid move- 
ment. It was impossible in watching this regular, rapid and 
graceful gliding movement, in which the whole body seems to 
take part like that of a coiling snake, to persuade oneself 
that one was not looking at an organized being, but at an 
agglutination of seminal filaments. The beat of the cilia 
