XX 
INTRODUCTION. 
That the function of Respiration should he widely dif- 
fused and very simple in these animals will follow from 
what has been said. The chylaqueous fluid, consisting 
largely of sea-water admitted freely from without, is itself 
a reservoir of oxygen, and thus its organized elements are 
perpetually aerated. We have already seen how the ciliary 
currents Avithin maintain a constant succession of the 
bathing fluid upon every part ; and there can be no doubt 
that some mode of exit is provided for the effete AAmter. 
What this is, however, I knoAv not. In Ceriantlms, which 
has a posterior foramen to the body-caAuty, I haA^e seen the 
water forcibly ejected from this aperture (see mfra, p. 272) ; 
I have also marked a sudden jet cVeau from the disk (pro- 
bably from the mouth, but of this I was not sure) of 
T. crassicorms, which shot up some mucous shreds Avith 
force to the surface, a height of some Aa'c inches. Perhaps 
these expulsions, and those from the tentacle-tips already 
alluded to, may be set doAAUi as so many expirations (per- 
haps periodical) of deoxygenated water. 
Ancillary to respiration, as renewing the Avatcr in the 
vicinity of the animal, is the ciliation of the external sur- 
face. This is strong and uniform on the tentacles, but 
I have never been able satisfactorily to trace it on the 
column. It is first Ausible at the margin, floAving in an even 
current up the tentacle, on every side, from the foot to the 
I saw with a lens, for an hour together, with the utmost distinctness, a 
small cii’cular (oval in perspective) foramen in each septum. That is, I saw 
them in a dozen or more successive septa, without interruptiou. The 
diameter of the foi’amen was about the same as that of a tentacle near the 
tip, in its ordinary state of extension. That the foramina were in films 
whose surfaces were coincident with the line of vision, and not transverse 
to it, I proved, by moving my eye to the right and left, by which the 
foramen became more and more round, or more and more linear, the line 
in the latter case being that of the axis of the column. Hence they must 
have been in films ruuuing from the column-wall towards the axis perpen- 
dicularly, as regards the position of the animal; — conditions which agree 
with the septa, and with them only. 
The next day, with a very favourable sight, I traced the foramina conse- 
cutively for half the circumference of the animal. In this space there 
were 49 septa (perhaps one more than the half, for I bisected only with my 
eye) ; and I found that the foramina are pierced through those which are 
entire (by far the greater number), but that the series is interrupted irre- 
gularly by those imperfect septa, which span the cavity like an arch. The 
latter were invariably two together, differing much in the height of 
the arch, and graduated in this respect. The detail of the numbers of the 
consecutive septa, in the half-animal, stands thus ; — 
Perforate — 13 . 2 . 10 . 4 . 2 . 2 . 2 . 
Imperforate — . 2.2 . 2. 2. 2. 2. 2 
