Exhibition of Sponges. 



237 



Association held in 1857, it was proved that the organs of 

 incnrrent action were situated within the large intermarginal 

 cavities, as in Grrantia 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 effected, 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 Spongiadce" 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 Tefliea, 

 Geodia, Dysidea, but confines each genus strictly within the 

 bounds indicated by the peculiar mode of the structure of the 



