403 Mr. J. S. Bowerbank on the Spongiadse, 



lessen the now almost insuperable difficulty that exists under the 

 present circumstances, in determining species by description. 

 I therefore propose in the first place to limit the genus Spongia 

 to such species only as strictly agree in the anatomical structure 

 of the skeleton with the two well-known species of the sponge of 

 commerce. 



In January 1841* I had the honour of reading before the 

 Microscopical Society of London, a paper " On the keratose or 

 horny Sponges of commerce," in which I have proved the soli- 

 dity of the fibre and the occurrence of spicula in certain portions 

 of it ; but at that time I had not been able to obtain the sight of 

 a specimen of either the Mediterranean or West Indian species, 

 in the precise condition in which they are, immediately after 

 being taken from their native element. Since then I have been 

 furnished by my friend Dr. Veronge with specimens of the West 

 Indian sponges of commerce, which were undoubtedly alive when 

 taken by him from the sea in the harbour at Bermuda, and some 

 of which were immediately immersed in spirit to prevent the rapid 

 discharge of the gelatinous interstitial matter. 



In addition therefore to my former observations on these ani- 

 mals, I may state, that in a living condition the West Indian 

 sponge is furnished with a thin, simple, and pellucid investing 

 membrane, in which there is imbedded, without any definite ar- 

 rangement, numerous simple single-pointed and simple double- 

 pointed spicula, among which triradiate spicula are occasionally 

 to be seen. 



In one of the specimens obtained by my friend Dr. Veronge 

 and preserved in spirit, the interstitial fleshy matter is very abun- 

 dant and of a considerable degree of density. It abounds with 

 siliceous simple single-pointed, simple double-pointed, triradiate 

 and other forms of spicula agreeing precisely in character with 

 those I have described in my paper pubhshed in the Microsco- 

 pical Society^s ' Transactions,^ as occurring imbedded in the large 

 flattened fibres of the sponge. There is no definite arrangement 

 of these bodies, but they appear thickly and irregularly dispersed 

 amid the gelatinous matter which fills up the whole of the inter- 

 stices of the fibre, excepting those spaces which form the tortuous 

 canals of the sponge. 



With this additional information regarding their anatomical 

 structure, I propose that the genus Spongia shall be limited to 

 those species only which shall strictly agree with the well-known 

 and legitimate types of the true Spongia, and that the following 

 characters be adopted to limit and distinguish the members of the 

 genus. 



Gen. Char. Skeleton composed of a network of keratose fibres 

 * Transactions of the Microscopical Society, vol. i. p. 32. 



