XLI. On the anatomy and physiology of the spongiadæ.—Part III. On the generic characters, the specific characters, and on the method of examination

Abstract

While the arrangement of other branches of natural history has occupied the attention of some of the most laborious and talented naturalists of every age, the Spongiadæ appear to have scarcely attracted sufficient attention to excite any writer on natural history to a serious attempt at a systematic classification. This neglect has not arisen from any incapacity for a definite arrangement on the part of the Spongiadæ, as the organic differential characters of the numerous groups into which, by careful examination, they may be readily divided are as varied and as widely removed from each other as are the strikingly distinct and well defined divisions of the Corallidæ; and the number of species I believe to be very much greater than those of the latter class. Of British species alone I am already acquainted with 150 or more; and new ones are continually being discovered by the aid of the dredge. It becomes therefore a matter of necessity that we should classify their permanent varieties of structure, and found on them a series of orders, suborders, and genera, and through these subdivisions become enabled to recognize more readily the very numerous species of these animals which abound in all parts of the world. De Blainville proposed to include the whole of the Spongiadæ under the designation of Amorphozoa; but this term is objectionable, as all sponges cannot be considered as shapeless—on the contrary, many genera and species exhibit much constancy in their form. Neither can the term be justly applied to their internal structure, as we find in Grantia , Geodia , Tethea , and other genera regular and systematical structures which are very far removed from shapelessness. I have therefore thought it advisable to adopt Dr. Grant’s designation of Porifera, a term which embraces the whole of the Spongiadæ, and which is truly descriptive of the most essential general action of the animal's power and mode of imbibing nutriment, which in every species with which I am acquainted is, by a series of minute pores distributed over the external membrane of the sponge.