408 Mr. J. S. Bowerbank on the Spongiade, 
its production in other and higher orders of the animal king- 
dom. Thus we find it in the foliated portions of a coral (Pavonia 
lactuca) when deprived of its earthy matter by dilute hydrochloric 
acid. In this case, the tissue occurs in the form of shorter and 
stouter filaments than in the sponge, and there is an attenuation 
of the fibre towards each of its ends; nor are the fibres so closely 
matted together as in the sponges, but on the contrary, there are 
frequently but a few filaments irregularly disposed amid the de- 
calcified tissues of the coral. I have also found it in the remains 
of a fleshy mass of what appeared to be an Ascidian, which was 
attached to a group of zoophytes. from Algoa Bay. It has also 
been shown, by Dr. Carpenter, that the decalcified shell of the 
common egg, and its membrana putaminis, are entirely com- 
posed of this peculiar tissue. In the latter instance the similarity 
is so great, both in the form of the structure and the mode of 
disposition, that it would be exceedingly difficult to distmguish 
between that derived from the sponge and the tissue of the mem- 
brana putaminis, if it were not that the fibres of the latter are 
somewhat less in diameter than those of the former. 
The imvesting membrane is generally exceedingly thin and 
pellucid, and without any trace of fibres or other forms of or- 
ganisation. 
CARTILOSPONGIA. 
Gen. Char. Fibre cartilaginous, imperforate, contaiming oat- 
shaped cavities thickly dispersed, from each of which numerous 
minute canals radiate to unequal distances. 
C. rigida. Sponge free, compressed, discoid. Fibre rigid, com- 
pressed ; longitudinal fibres radiating from the centre towards 
the circumference; lateral fibres at right angles to the longi- 
tudinal ones, forming square or oblong interstices. Excurrent 
canals, on the marginal edge of the sponge, few and irregularly 
disposed. 
The general aspect of the fibre of this sponge is very like that 
of decalcified foetal human bone from the cranium, but the fibre 
is somewhat more compressed. 
When a few fibres, immersed in water, are examined by trans- 
mitted light with a power of 100 linear, it is seen that every 
part of their substance contains minute oat-shaped cavities, re- 
presented by Pl. XIV. fig. 7, and which correspond exactly, im 
form and mode of disposition, with the analogous minute cavities, 
miscalled corpuscles, which abound in such quantities, and are 
so well known to every anatomist as peculiarly characteristic of 
true animal bone. In the latter, when viewed with a high micro- 
scopic power, there may be observed a profusion of exceedingly 
minute radiating canals, which are said to communicate with the 
