444 Dr. J. E. Gray on the Classification of Sponges. 



intermediate between the orders — as, for example, Mr. Carter 

 has described a Tethyoid sponge which has the defensive spi- 

 cules of the Hamispongia^ and there are some sponges which it 

 is difficult to say if they belong to the Astrospongia or Sphcero- 

 spongia ; but such annectent or intermediate genera are found 

 in all methods of arranging animals and plants. Dr. Bower- 

 bank and Prof. Oscar Schmidt form genera for single species 

 or for small groups of species, and at the same time place 

 beside them genera of a most polymorphal character, contain- 

 ing an abundance of species, which would break up into natural 

 groups having characters quite as marked as those which 

 distinguish the limited genera which they admit. But all this 

 must be left to younger eyes. 



Some sponges have the habit of collecting and imbedding 

 in their skeleton or sarcode spicules which are the remains of 

 other sponges that have died and decayed in the sand on the 

 sea-coast on which they live. Some species are so particular 

 that they select one or more special kinds of spicules for this 

 purpose ; therefore it is necessary to determine with care the 

 real spicules that naturally belong to the organization of the 

 sponge and those that have been added to it. 



It has been repeatedly stated that the external form of 

 sponges does not aiford any character for their distinction, and 

 that they can only be distinguished by their microscopic 

 structure. It is quite true that the microscopic structure and 

 the form and arrangement of the spicules do afford most im- 

 portant characters for the distinction of the sponges, as they 

 do in all other natural and artificial bodies ; but the external 

 character is quite as important, and the two together must be 

 studied before a natural method of classifying these animals can 

 be arrived at. This fallacy has arisen from the sponges having 

 of late been chiefly studied by microscopists : since they found 

 that the spicules form very pretty slides, of course they con- 

 sidered their method of study was the only one to be followed. 

 I think no one can look at an extensive collection of sponges 

 without being struck by the persistence of the forms which the 

 species assume, and how the species naturally fall into groups 

 according to their external form ; and it is curious to see that 

 the microscopists who write most strongly against any atten- 

 tion being paid to the external form, are themselves influenced 

 by it in the formation of their genera. It is very true that some 

 species are very polymorjihous, as, for example, the Voluspa 

 polymorpha of Miklucho-Maclay, from the North Pacific 

 Ocean ; but there are polymorphous species of Algae and zoo- 

 phytes, and yet the general forms of these animals and plants 

 are used in their arrangement, and the polymorphism, as in this 



