with descriptions of some new genera. 401 



racters than those which have hitherto designated the numerous 

 and extraordinary species of these singular animals. 



Lamouroux^ in his *IIistoire des Polipicrs Coralligenes Flex- 

 ibles/ has described 163 species of Spongiada under the common 

 generic designation of Spongiaj basing his descriptive characters 

 principally upon form and colour. It is almost unnecessary for 

 me to say, that there is scarcely one of these descriptions which 

 can be applied with any degree of certainty when we attempt to 

 identify specimens of recent sponges. 



Dr. Fleming, in his ' History of British Animals/ taking ad- 

 vantage of the valuable labours of Dr. Grant, has divided the 

 Spongiadce into a series of genera founded, to a certain extent, 

 upon their anatomical structure, and taking the common officinal 

 sponges as his type, has described the characters of the genus 

 Spongia in the following words : — " Porous, the cartilaginous 

 skeleton simple or destitute of earthy spicula.^^ 



Dr. Johnston, in his admirable ^History of the British Sponges 

 and Lithophytes/ has added considerably to these characters, 

 and has thus designated the genus : — " Body multiform, very 

 porous, elastic, composed of a network of corneous fibres inos- 

 culating in every direction, and traversed by tortuous canals 

 opening on the surface by wider orifices ; the fibres often con- 

 tain imbedded spicula : gelatine fugacious : marine." This se- 

 ries of characters would perhaps be sufficiently definite if we 

 had to consider the British species of the Bpongiadcu. only, but 

 when we launch into the wide field of exotic species, it ceases to 

 be sufficiently descriptive and definite to enable us to hope to 

 arrange these extraordinary and protean forms of animal life in 

 such a manner as to allow the student to recognise a species, or 

 to refer it to its proper genus with anything approaching to the 

 same degree of certainty that we find the constant practice in 

 the science of botany. 



It is true that in the latter science we have a much more ex- 

 tended series of determinate structural characters than we can 

 ever hope to find among the Spongiadce, and that among plants 

 these characters are of such a nature as to be readily available 

 either to the unassisted vision or by the aid of a low microsco- 

 pical power ; while among the Spongiada, from the minuteness 

 of many of the most essential organs, we can scarcely hope to 

 make any great degree of progress in the knowledge and deve- 

 lopment of such characters without the aid of the best modern 

 microscopical powers ; but with such assistance there is little doubt 

 in my own mind, from the great and permanent varieties of the 

 structures of the skeleton especially, that we shall be enabled to 

 establish such a series of well-defined new genera, and to subdi- 

 vide and ari'ange those already established, as very materially to 



