326 DR.J.S., BOWERBANK ON SILICEO-FIBROUS SPONGES. [May 13, 
hexangular pores, lined with a thin layer formed of elongate fusiform 
spicula, placed parallel in bungle in a more or less longitudinal 
direction round the inner mouth of the pores.” The whole of this 
latter description of the structure of the sponge is remarkable for its 
inaccuracy. He repeats the fallacy that ‘the sponge is formed of 
small spicula,” and describes their inosculation, when no such inos- 
culation ever takes place among true spicula, He describes the 
pores in the total absence of the dermal membrane, evidently mis- 
taking the incurrent orifices of the skeleton for those organs, and 
then he lines the cavities ‘‘ with spicula placed parallel in bungle.” 
What may be the mode of disposition of spicula in bungle I must 
leave my readers to imagine, as I really cannot conceive their arrange- 
ment under such circumstances, and especially as I have been totally 
unable to detect any such lining of spicula within the orifices de- 
scribed by Dr. Gray. 
The sponge, of the natural size, and slightly magnified, has been 
beautifully represented in plate 11 of the ‘ Proceedings of the Zoolo- 
gical Society’ for 1858. 
The natural surface, and the whole of the dermal system of this 
sponge, have been entirely destroyed, and the pores are therefore un- 
known to us; but from the regularity of the size and mode of dis- 
position of the incurrent orifices of the skeleton, it is very probable 
that they were congregated immediately above them. Within the 
sponge, on the surface of the great cloacal cavity, there are a series of 
large areas for the discharge of the excurrent streams into the cloaca ; 
they are very like in size and form to those of the inhalant surface, 
but they are destitute of the elaborate defences that characterize the 
inhalant organs, Fig. 4, Plate XXI. represents one of these areas 
x 108 linear. 
The form and mode of disposition of the oscular area readily in- 
dicates the congregation of the oscula after the same manner as that 
indicated in Alcyoncellum speciosum, and as exhibited in various 
species of Geodia. The reticulation-fibre closing this area in the 
sponge under consideration is remarkably complex and beautiful ; 
each fibre of the oscular area is a compound structure. Whena 
portion of it is immersed in Canada balsam, and viewed by a micro- 
scopic power of about 150 linear, it is seen to be a complete cylinder 
formed of a dense network of siliceo-fibrous structure, produced on 
the same radial principle as that which prevails in the skeleton of 
the sponge, but in consequence of the small elongate cylindrical 
space in which it is developed, its structure is necessarily very con- 
fused; yet the indication of radial fibres within it are sufficiently * 
apparent to assure us of this fact. On the surface, and within the 
reticulations, there were a few very slender, smooth, acerate spicula 
which, from the mode of their disposition, are evidently the tension- 
spicula of the membranous tissues of the sponge. From the ex- 
ternal surface of the compound fibre there were a few basal portions 
of, apparently, hexradiate auxiliary fibres projected; but none of 
them were developed to the extent of the production of the rectan- 
gulated lateral fibres. The external fibres of this beautiful com- 
