56 Mr. W. J. Sollas on two new and 
tion and to the embryos of the Clona. On the other ‘hand, 
however, in the embryos of Cliona no wisp-like cap has been 
observed; and no known embryo of Cliona or of any other 
sponge exhibits the regular and close arrangement of spicules 
which is to be seen in the walls of our structures; the spicu- 
lation of the young Cliona is in the highest degree confused, 
presenting no trace of order or arrangement. ‘These facts are 
sufficiently important; but when in addition we find the dia- 
phragms, as we may as well call them at once to avoid peri- 
phrasis, exhibiting such a great diversity of form and size, and 
this always in exact correspondence to the size and shape of 
the orifices or tubes they occupy, and when, moreover, we 
find them invariably attached to the sides of these tubes or 
orifices by one circumferential edge, we must, I think, exclude 
from the question all notion of attributing an embryonic nature 
to them. 
There then remains, so far as I can see, only the other 
alternative ; and the facts which tell most strongly against the 
previous supposition are just such as lend most support to this, 
the complete justification of which is to be found im the con- 
stancy with which the diaphragms occur just at the apertures 
of communication between adjoming chambers and no where 
else. This is an adaptation which Mr. Carter tells me is not 
to be found in the case of the embryos of Cliona; but there 
can be no doubt about its existence here. By an observer 
examining the chambers of our Cliona for the first time, it 
might perhaps be for a moment called in question, since on 
looking into one of these chambers one may sometimes see, as 
if simply adhering to its walls, some four or five diaphragms 
looking just like so many limpets seated on the walls of a hole 
in a rock, and giving one no hint as to the existence of aper- 
tures concealed beneath them; if now, however, we remove 
these little bodies one by one with a fine needle, we shall 
disclose beneath each a corresponding opening leading directly 
into an adjoining chamber. This experiment I have per- 
formed several times, and always with the same result. That 
these organs are peculiar to the constricted apertures can 
therefore admit of no reascnable doubt; and their dia- 
phragmatic nature seems to follow as a matter of course. 
Why such diaphragms should exist, what is their precise 
function in the economy of the sponge, is another question, 
and one to which, in the absence of accessible evidence, I do 
not feel much inclined to hazard an answer ; though if one 
must conjecture, one might suggest that they may act like the 
fixed ventilating partitions in a mine, shutting off communi- 
cation in some directions, leaving it open in others, and so 
a] 
