124 REPORT—1857. 
languidly forth (fig. 5). On examining the pores I could not find a single 
one open. 
I again examined the same sponge at 8 p.m. of the 16th October. » The 
excurrent tube bearing the osculum was nearly erect (fig. 6), and the stream 
was slowly pouring forth. I examined the usual part for the pores, and found 
very few that were in a slight degree opened. I then directed my attention 
to the thin stratum by which the sponge was attached to the watch-glass. 
Hitherto I had not detected any pores in that part of the sponge, but’ this 
evening I saw several which were open, and into which the floating mole- 
cules were steadily entering. I selected one spot for observation, where 
there were several pores indistinctly visible: in about 5 minutes they became 
very much more distinct, fully expanded, and the margins assumed a thick- 
ened and well-defined outline; others made their appearance, and at last 
fourteen were in a fully expanded and active state (fig. 8). I immediately 
put a drop of water charged with indigo over the pores; the molecules were 
absorbed with great rapidity, and the rush of the indigo to the pores became 
so great that its accumulation rendered the sight of them indistinct, and to 
clear the sponge from the indigo I sent a puff of air from my mouth on to 
the surface of the water in the watch-glass, but doing this rather too roughly, 
I turned the sponge over on its flexible base, as it were on a hinge; I there- 
fore removed it and placed it in a basin of fresh water to float it back again 
into its proper position, and immediately replaced it under the microscope, 
the whole operation not occupying more than a minute; but on getting the 
precise spot into focus, I found not a single pore open: the sudden violence 
done to the sponge had caused a complete cessation of action and a perfect 
closing of the inhalent pores. ‘This result is curious, in contrast with the 
fact, that the sponge endures a large Vibrio, which is continually crawling 
with considerable activity over its surface, and frequently biting large mouth- 
fuls out of the soft tissues, without appearing to create the slightest alarm, 
although passing immediately across the pores while in full action. 
18th October.—At 11 p.m. I resumed my observations at the precise spot 
which I had examined on the evening of the 16th, and of which I then took 
asketch. Not one of the pores that I had carefully diagrammed opened 
during an hour anda half that I constantly observed them, but several others 
close by the spot were fully expanded, and were steadily imbibing the mole- 
cules of indigo with which I supplied them. I selected three of these for 
observation, but with a power of 260 linear I could not detect cilia. The 
mode of the entry of the molecules was regular and very remarkable: they 
approached the pore by a steadily accelerated motion, and when they reached 
the margin rushed suddenly into the orifice; but although entering thus 
forcibly, their course was not straight downwards, but each one seemed to 
slip as it were round the margin and pass rapidly off at an angle of 45 degrees 
immediately beneath the dermal membrane, and their course might be traced 
for a considerable distance in a straight line, and with a gradual decrease of 
speed from the moment of their entrance. These circumstances would seem 
to indicate the position of the motive power to be immediately within the 
margin of the pore, but I could not in any case detect them; I sometimes 
saw a hazy rim immediately within the pore, but I believe this was due to 
parallax arising from a slight change in the position of the dermal mem- 
brane. The peculiar mode of the entry of the molecules, combined with the 
cyclose circulation that I have previously noted as occurring when the in- 
halent action became languid, induces me to believe that the seat of the cilia 
is confined to the large intermarginal cavities of the sponge, and that they are 
not appendages of either the pores or the oscula. At the end of an hour and 
