500 DR. J. E. GRAY ON SPONGES. [May 9, 



species in these genera have the spicules of that form, or with the 

 forms so combined together. The modification of the forms and the 

 comparative sizes of tlie different forms as combined together afford 

 good characters for the distinction of the species of the genera or 

 subgenera. 



There are more genera than I would willingly have made without 

 more materials ; but I could not exhibit the system which I wished 

 to propose without forming some genera on very imperfect materials, 

 as on a bihamate spicule figured in Bovverbank's 'British Sponges.' 



I have no doubt that some, indeed many, zoologists will complain 

 of the numerous genera into which the sponges are here divided ; 

 but I believe that sponges will never be properly distinguished into 

 species until they are even more closely divided into genera or sub- 

 genera than is here proposed. At least this has been shown to be 

 the case with Diufomacecp, dlgce, and the animals which require the 

 microscope to distribute them into groups or species. 



No part of the sponge seems so well adapted for the purpose of so 

 dividing them as the S])icules that form their skeleton, which afford, 

 both in their form and in the combination of one or more forms of 

 the same kind, the best characters for the separation of the sponges 

 into genera and the distinction of the species. 



I may state that many of the names used for the genera have no 

 derivations, but are mere fortuitous combinations of letters, so that 

 compilers of indices of genera need not attempt to find derivations 

 for them, or to correct the formation of some of them, as being more 

 consistent with the derivations they may gratuitously assign to them, 

 as has been done with some generic names of the same kind by 

 Agassiz and others. 



It is only necessary to look at Dr. Bowerbank's work on ' British 

 Sponges,' to show that some other system than that which he has 

 adopted is necessary; for out of 193 species of British sponges no 

 less than 43 are referred to the genus Isodictya, 42 to Hymeniaci- 

 don, 28 to Halichondria, and 11 to Dictyocylindrus ; so that 124 

 are referred to four genera, and the remaining 69 species are divided 

 into 2C genera. 



Class PORIPHORA. 



Spongia, Linn. 



AmorpJwzoa, Blainville, Manuel Act. 1821. 



Forip)hera, Grant, Outlines of Anat. 1841. 



Porifera, Bowerbank, Phil. Trans. 1850j p. 18G ; Brit. Sponges, 

 18G2; Carpenter, Microscope, p. 53G (not Hogg, Ann, & Mag. N. 

 H. 1840, iv.). 



Poi'ophora, Hogg, Ann. & Mag. N. H. 1840, iv. 



Gelatinifera, Hogg, Ann. & Mag. N. H. 1840, iv. 



Spongioitista, Hogg, Athenseum, 1867, p. 160. 



Sponyiadxe, Bowerbank, Brit. Sponges, 1864. 



The sponges consist of a flesh or sarcode formed of aggregations 

 of cancebaASkQ bodies, some of which are furnished with one or more 



