122 REPORT—1857. 
pressure outward of the newly-formed radial lines of the skeleton. Ata short 
distance within the margin, and in the neighbourhood of the newly-produced 
portion of the sponge (4, fig. 1), there was a single osculum situated on a 
large oval bladder-shaped projection of the dermal membrane, which varied 
considerably in its form according as the sponge was inert or in action. 
When in the former state it was frequently in a semi-collapsed condition, 
the apex being considerably attenuated, so that the whole assumed an ovate 
form, the smaller end being the distal one, and in that condition not the 
slightest orifice was visible, the osculum being entirely closed, and what was 
very remarkable, its place was not even indicated by an apparent thickening 
or corrugation of the membrane. On the contrary, when in action the blad- 
der-shaped projection was dilated at the apex so as to cause it to assume a 
regular oval form, and the osculum was apparent in the form of a large cir~ 
cular orifice, about one-fourth the size of the diameter of the bladder-like 
portion on which it was situated (fig. 2). From this orifice a powerful 
stream of water was continuously ejected, and large and small patches of 
feecal matter were frequently thrown out with considerable force. 
When a small portion of pure indigo was rubbed up in water, and a 
drop or two of the water laden with this substance was mixed with that in 
the watch-glass, and it was placed beneath the microscope with a power of 
130 linear, and a strong light passed through it from a concave mirror, 
at first no’ action was apparent, the osculum was in a completely closed 
condition, and although I searched the surface of the newly-formed portion 
of the sponge with the greatest care and attention, I could not detect a single 
open pore. In rather more than half an hour I found one open, and in a 
short period others gradually and successively made their appearance, until 
at last, in one of the spaces between two of the radial lines of the skeleton, I 
readily counted as many as 10 in a fully expanded and active condition, and 
in other similar spaces they were apparent in considerable numbers. The 
action presented to the eye was exceedingly interesting. The molecules of 
indigo approached the surface of the sponge at first slowly, their motion 
being gradually accelerated as they became nearer, until at last they sprung 
as it were with avidity into the pores; within the sponge some passed to the 
right hand, while others took their course to the left, and they often passed 
other molecules which had entered by other pores, and which were passing 
in a contrary direction. Many of these molecules might be readily followed, 
as they meandered through the interior of the sponge, and might be seen 
flowing in every direction. During the maintenance of this action in full 
force, when I directed my observations to the osculum, it was seen pouring 
forth a continuous stream of water and along with it masses of flocculent 
matter, and many of the larger molecules of the indigo that had entered by 
the pores; but it is remarkable that although the finer molecules of indigo 
were being imbibed by the pores in very considerable numbers, very few 
indeed of them were ejected from the osculum; and if the imbibition of the 
molecules continue for half an hour or an hour, and then cease, the sponge 
is seen to be very strongly tinted with the blue colour of the indigo, and it 
remains so for at least 12 or 18 hours, after which period it resumes its ori- 
ginal pellucid appearance, the whole of the imbibed molecules having under- 
gone digestion in the sarcode lining, the interior of the sponge and the effete 
matter having been ejected through the osculum. After having watched 
the active operations of the sponge for nearly an hour, I set to work to sketch 
the field of view in the microscope, in order to mark the position of the 
pores; but by the time the outline of the sketch was completed, about half 
an hour, the action had ceased, the pores were entirely closed, and my further 
