vi PREFACE. 



The physiology of the sponges has been fully elucidated 

 by the industry and talent of Professor Grant; and Mr J, S- 

 Bowerbank has entered on an investigation of their minute 

 and varied anatomy which will probably lead to a new and 

 more stable arrangement of the class. My aim has chiefly 

 been to make myself acquainted with the variety of species 

 which inhabit the shores of Britain ; and to enable others 

 to obtain, with comparative facility, the same acquaintance 

 with them is the object of this volume. For this purpose 

 I have in general added to my own account of the species, 

 the original descriptions of them given by other authors, 

 more especially by Colonel Montagu; and I have illus- 

 trated these verbal delineations with a series of portraits 

 drawn from life, and resembling the originals as closely as 

 the pencil of my wife could make them. But these repre- 

 sentations will only lead to error if due allowance is not 

 made, in the comparison of them with specimens, for those 

 differences which Nature has herself impressed on every in- 

 dividual, — no two specimens of any species being ever found 

 exactly alike in external figure ; and to represent their mi- 

 nute, albeit specifical, differences of texture is sometimes 

 impossible. Colonel Montagu felt this difficulty so strong- 

 ly that he has given figures only of those species " which 

 possess sufficiently strong specific characters to be defined 

 by the pencil." 



It is, I think, Sir James E. Smith who dwells so point- 

 edly on the pleasure that a naturalist has in sharing his dis- 

 coveries and his specimens with other naturalists of congenial 

 dispositions and pursuits ; and, to judge from my own ex- 

 perience, there are many eager to participate in this plea- 

 sure. With a liberality and frankness which it is easy to 



