Exliihition of Sponges. 
237 
Association held in 1857, it was proved that the orgaDS of 
incnrrent action were situated within the large intermarginal 
cavities, as in Grantia ciliata, and not immediately around 
or within the pores. The vigorous imbibition and ejection 
of the surrounding water was as strikingly indicative in the 
fresh-water sponge, as it was in the marine one, of the 
period of feeding ; while the languid action in either case 
distinctly marked the aerating process only, during which 
the digestion of the nutritive particles previously imbibed is 
gradually efiPected, and the effete matter partially ejected. 
The structure of the pores, and the perfectly plastic nature 
of the dermal membrane, as exhibited in these observations," 
Dr Bowerbank says, " are very remarkable. The sensitive- 
ness of the sponge to injury, the rapidity of the act of closing 
those organs, and the power they appear to possess of opening 
new ones to any extent, and in any direction they please, 
attest an astonishing amount of vital energy in a membrane 
in which he had been unable to trace any indication of the 
existence of fibrous tissue." 
On the 18th of June 1857, a paper was read before the 
Koyal Society of London, " On the Anatomy and Physiology 
of the Sjpongiadce," By J. S. Bowerbank, LL.D., F.E.S., &c. 
In that highly valuable and original monograph. Dr. Bower- 
bank points out the faulty system of Lamarck, founded upon 
external form, "inasmuch," he says, " as there is no class of 
animals in which the form varies to so great an extent, 
according to the difference of locality, or other circum- 
stances." He remarks " that the division of the Spongiadce 
by their chemical constituents, adopted by Fleming, Grant, 
Johnston, and other modern naturalists, may serve very well 
to separate them into primary groups, but that these are far 
too limited to be applied as generic characters." He there- 
fore rejects both systems, retaining the latter for forming 
primary divisions only, and proposes founding the generic 
characters principally on the organic structure and mode of 
arrangement of the skeleton. Dr Bowerbank accepts all the 
well-established genera of his predecessors, such as Tetliea^ 
Geodia, Bysidea, but confines each genus strictly within the 
bounds indicated by the peculiar mode of the structure of the 
