ON THE VITALITY OF THE SPONGIADA, 123 
proceedings, as regarded their delineation, were deferred to a more favourable 
opportunity. . 
~ On the 14th the sponge was in a quiescent state, and strongly tinted by 
the indigo imbibed on the previous evening. 
15th October.—I examined the Spongilla at 4 past 10 A.M.; there was-no 
action to be detected, and a considerable tint of colour was still visible: at 
9 p.m. 1 placed it under the microscope; it was then free from colour and 
in full action. The tube bearing the osculum was very different in form 
from what it was on the evening of October the 13th, when at 11 P.M. it 
was in form and proportions like an olive (fig. 2); at 9 p.M., on the 15th, it 
was in form and proportions like the last two joints of a man’s finger, slightly 
bent at the last joint (fig. 3). At 10°30 of the same evening, when the 
action had grown very languid, the basal portion was very much expanded, 
and the whole assumed the form of a cone, the apical portion of which had 
fallen over on one side, and the excurrent stream was directed towards the 
body of the sponge at an angle of about 45 degrees to its plane (fig. 4); it 
is evident, therefore, that this organ assumes a great variety of forms. 
At 9 p.m., when I commenced my observations, the portion under exa- 
mination was crowded with pores in a fully expanded condition, and I imme- 
diately mixed a drop of water charged with indigo, with that in the watch- 
glass, and the imbibition of the molecules continued steadily until 10°30 P.M., 
when it suddenly became very languid; at this period I directed my atten- 
tion for a few moments to the osculum, and on again returning to the obser- 
vation of the pores, I found nearly the whole of them completely closed. I 
examined some of the largest of the pores with the utmost care for more than 
an hour with a power of 260 linear, but I could not detect cilia either at the 
margins or within the entrance. When the incurrent action became rather 
languid, I observed that the molecules within the sponge were performing a 
sort of cyclose circulation, frequently rising up and passing across the open 
pores, but never coming out through them; but while this action was going 
forward, now and then a molecule of indigo would pass languidly into the 
pore. It would seem, therefore, to indicate that the organs of incurrent 
action were situated, as I have long suspected, within the large intermarginal 
cavities, as in Grantia ciliata, and not immediately around or within the 
pores. 
During the continuance of vigorous incurrent action, the water charged 
with indigo is in continual motion, flowing from all quarters towards the 
open pores ; many of the molecules come in contact with the portions of the 
skeleton projected through the dermal membrane, and wherever they touch, 
they adhere tenaciously to the adhesive matter coating those parts, in the 
same manner as they do to the sarcodous membranes within the sponge ; but 
the same results do not seem to follow with those without, that occur with 
those within. On the evening of the 15th, when I terminated my observations, 
T left the sponge with an abundance of molecules attached to the internal 
tissues, and a considerable quantity of similar molecules fixed to the external 
fasciculi. On examining the same sponge at 11 a.m. on the 16th, I found 
the external tissues with the molecules still adhering in considerable quan- 
tities, but the internal ones were perfectly free from the coloured particles. 
The excurrent tube still retained much the same form that it had on the 
termination of my observations on the previous evening, but it was in a more 
collapsed condition, and instead of the osculum being a well-defined circular 
orifice, it had assumed a much smaller and more irregular shape, and was 
puffed out from the end of the excurrent tube in the form of a loose hemi- 
spherical appendage to its apex, from which a molecule now and then came 
