Microscopic Journal, and Structural Record . ansed from the chalk, by immersion in dilutemuriatic acid, until effervescence ceases, the deep circular orifices willfrequently be seen to have spicula projecting from their sides ; thusstrongly pointing them out as having been, in all probability, themouths of the larger ex-current canals. If small pieces, about a quar-ter of an inch in diameter, be now selected, presenting the roughest Society, Jan. 27,1841. (Seep. 8.) Since the publication of these facts, I have also as-certained, from the examination of an Australian species of Keratose sponge,
Microscopic Journal, and Structural Record . ansed from the chalk, by immersion in dilutemuriatic acid, until effervescence ceases, the deep circular orifices willfrequently be seen to have spicula projecting from their sides ; thusstrongly pointing them out as having been, in all probability, themouths of the larger ex-current canals. If small pieces, about a quar-ter of an inch in diameter, be now selected, presenting the roughest Society, Jan. 27,1841. (Seep. 8.) Since the publication of these facts, I have also as-certained, from the examination of an Australian species of Keratose sponge, whichwas brought by Mr. Gould from Swan River, preserved in spirit immediately afterbeing taken from its place of growth, that silicious spicula occur in great numbersin the fleshy substance that fills up the horny network of the sponge in its livestate. It therefore ceases to be an anomaly, as it might have hitherto been sup-posed, that silicious spicula should be found imbedded in the fossilized remains ofa Keratose sponge.—March 102 ON THE SILICIOUS BODIES OF CHALK, ETC. and most saccharine aspect, and these be illuminated by a leiberkuhn,and examined with a microscopic power of 120 linear, under favourablecircumstances, it will be seen that the surface is formed by a complexmass of small contorted tubuli, the apices of many of them being fur-nished with a minute perforation, as representedin Fig. 2.* The tubuli on the surface of the flintstand boldly in relief from the more solid portionof the white crust, which surrounds the dense andsemi-transparent mass. If we give but a slightconsideration to the circumstances under whichthese bodies have been probably buried, we shallat once perceive that the characters exhibited bythe surface of the flints, and the state of the tissues at this part, areexactly such as we should naturally expect to be the case; for if amodern sponge of a close texture be immersed in water, in a tranquilsituation, and a gradual deposit of calc
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