339 
and Functions of the Sponge. 
hitherto examined, pores, for the lodgement of certain small 
moving powers, and for the admission of water into the interior, 
are as distinctly seen as on the general surface of the sponge. 
I have frequently cut olf all the papillae from the surface of a 
living sponge, without thereby occasioning the slightest inter- 
ruption or retardation of the currents from that sponge. And 
currents have always continued to flow as quickly, and for as 
long a period, from orifices, deprived of their projecting conical 
papillae, as from the orifices, on which the papillae had been left 
entire. I have often taken specimens of the Spongia compressa , 
which had only one opening at the extremity ; and on cutting 
off their peduncle, so as to lay them open at both ends, I have 
always found, on placing them under the microscope, with sea- 
water, that they sent forth a current, equally powerful, from the 
artificial, as from the natural orifice ; and, indeed, a transverse 
section, taken out from the middle of this animal, by cutting off 
both its ends, when placed under the microscope, is seen to pour 
forth a languid stream, from both extremities. These circum- 
stances sufficiently shew, that there is nothing in the structure 
or properties of these orifices, that is at all necessary to the ex- 
istence of the currents which issue from them ; and the only ef- 
fects which a papilla can possibly have on the current from it, 
are to convey that current a little off from the general surface 
of the animal, and to add a little more water to the entire stream, 
by the minute currents of the pores, distributed every where 
over the surface of the papilla itself. 
As the Spongia cristata , or Cock’s-comb Sponge, was the 
species concerning which Mr Tallis and Dr Knight stated, in the 
Transactions of the Royal Society of London for 1765, that 
they had seen the fecal orifices Contract and dilate themselves 
when they examined it alive in a glass of sea-water on the coast 
of Sussex, I have examined with particular care the phenomena 
exhibited by this animal in the living state. Neither on the sides 
of the boulders, where it is met with at Leith and Prestonpans 
Bay, nor when favourably placed in a vessel of sea- water, have 
I ever observed it contract or dilate its orifices. I have fre- 
quently examined its apertures with the microscope, both while 
they were left uncovered, and when they were still carrying on 
Rieir currents under water, but they have always remained quite 
