Nature of the Spongilla friabilis. 27? 
collapse of their very soft margins. By placing a thin layer, cut 
from the surface under the microscope, we perceive that each 
pore, besides its projecting defending fasciculi, has its margin 
supported by loose spicula lying parallel with the surface, and 
placed round the opening. The bounding fasciculi of the pores 
consist of so few spicula, and these are so loosely connected to- 
gether, that the whole surface wants the compactness which they 
produce in the marine sponges. These openings are not the 
cells of polypi, nor can we discover by the microscope any trace 
of cilise on their margins ; but their whole internal parietes are 
closely covered by the same minute, granular bodies which line 
the pores and canals of the marine sponge ; and on viewing these 
bodies sideways, we observe that they project from the margins 
towards the centre of the openings, more distinctly than in most 
of the latter zoophytes. By examining their horizontal sections 
taken successively from the same part of the spongilla we discover 
that its pores are only the open entrances to canals which mean- 
der through the body, enlarging in their diameter as they pro- 
ceed, till they again reach the surface. The wide extremities of 
the canals are the fecal orifices, which are seen of uncommon 
magnitude, opening on the depressed parts of the surface between 
the lobes. The granular bodies which line the whole of these 
canals from the pores to the fecal orifices, are connected with 
each other, and with the parietes, by means of a very soft, trans^ 
parent, green-coloured, glistening matter. There are obviously 
fewer granular bodies on the surface of this gelatinous matter at 
the fecal orifices than elsewhere ; and when we examine it with 
highly magnifying powers in that situation, it appears quite ho- 
mogeneous, without fibre or grain in its texture. The internal 
canals are every where bounded and supported by the longitu- 
dinal fibres, and by single transverse spicula, which pass across 
from one fasciculus to another ; at the extremities of the canals 
the projecting, erect, longitudinal fibres have a slight convergence, 
both around the pores and fecal orifices. The single transverse 
spicula which bind together the longitudinal fibres, are almost in- 
visible to the naked eye ; hence in dried specimens of the Spon- 
gilla friabilis, the whole skeleton appears to be composed solely 
of longitudinal fasciculi, rising from the base, and branching to- 
wards the surface. These two kinds of fibres are connected 
