62 
TOMOPTERIS 
and the alimentary canal is thrown by this contraction into convolutions, which are 
sometimes slight and easily distinguishable, as shown in Plate VII. fig. 2, but which, 
when the caudal appendage is greatly contracted (as shown in figs. 6 & 7 of Plate LXII. 
vol. xxii.), may be so close as to render it difficult to follow their course, by reason of the 
opacity which the part then acquires. The part of the intestine contained in the caudal 
■ 
prolongation has its external surface clothed with cilia; but these are most apparent 
along particular bands. Cilia are also distinguishable on certain parts of that innermost 
layer of the general integument which forms the external boundary of the perivisceral 
space, their action being especially apparent near the ends of those lateral appendages 
which give support to the pinnulse. By the agency of these cilia a more special move- 
ment is imparted to the corpuscles of the fluid contained within the perivisceral cavity, 
than that which they receive from the movements of the body generally, and from the 
peristaltic contractions of the alimentary canal. Although these corpuscles, which are 
usually of a spheroidal form and of a diameter of about Toooth of an inch, very com- 
monly float singly, they are often to be seen aggregated in smaller or larger numbers 
into masses, which sometimes attain a considerable size (fig. 10) ; and we cannot doubt 
that the bodies supposed by Mr. Huxley to be young spermatozoa (p. 359, vol. xxii.) 
were of this nature. 
We have given much attention to the ciliated canals, first observed by Leuckart and 
Pagenstecher, which originate in two orifices near the base of the lateral appendages of 
each side (figs. 7, 8. a, b) on their dorsal aspect, and which then rapidly incline towards each 
other, so as to converge into a single canal, that runs along for some distance in the wall 
of the body, and then terminates in the perivisceral cavity (fig. 7. e). One of these orifices 
(a) is situated in the centre of a sort of rosette*, marked by radiating ridges furnished 
with large cilia ; the other (b) has round it a smaller rosette, which does not possess any 
such ciliated ridges. These ciliated canals are obviously the tiomologues of those which 
attain so much greater a complexity in the higher Annelida (the " segmental organs " 
of Dr. T. Williams). Although they are represented by Drs. Leuckart and Pagenstecher 
as existing in their specimens on every one of the pinnulated appendages, and even in the 
bases of the second antennae, we can state most positively, both from the observation of 
numerous living individuals, and from the evidence of well-preserved specimens now be- 
fore us, that, in the form of Tomopteris observed by us, they do not exist in the five lateral 
pairs which immediately follow the second antennae. And this fact is the more remarkable, 
since, as will presently appear, there is a stage in the animal's life at which it does not 
possess more than five pairs of pinnulated members, and in which, therefore, it is entirely 
destitute of ciliated canals. The direction of the ciliary current always appeared to us 
to be from without inwards (as affirmed by Leuckart and Pagenstecher, in opposition to 
what is generally stated on this point) ; and we repeatedly witnessed the passage through 
the canals, m this direction, of spermatozoa which had been emitted from the testes into 
the surrounding water. 
Each of the pinnulae, in our specimens of Tomopteris, presented (fig. 7. d, cl) the peculiar 
* This rosette was noticed by Busch , but he only imperfectly made out the canal of which it is the entrance. 
