Vlll PREFACE. 



ceeding variety and beauty of their structure, and are 

 thence induced to investigate the living actions of organs 

 so numerous, varied, and beautiful as those displayed to us 

 by a careful examination of their structure. With these 

 difficulties surrounding ray earliest attempts at the recog- 

 nition of species, and with a rapidly increasing knowledge 

 of the variety and beauty of the tissues which presented 

 themselves, as I proceeded with my investigation I felt 

 the necessity of abandoning external form and colour as 

 descriptive characters, and determined patiently to work out 

 a series of descriptive characters based on the peculiarities 

 of anatomical structure, and thus it is that in accordance 

 with the necessities of this preliminary labour, the introduc- 

 tion to the history of the British species has become di- 

 lated into an attempt at a general history of the anatomy 

 and physiology of the whole of the Spongiadae. 



The accomplishment of this task would have been com- 

 paratively hopeless without the very kind and liberal assist- 

 ance of numerous friends 



To the late Dr. Ayres, of the Mauritius, I am indebted 

 for a very interesting collection of sponges from that 

 locality ; and to Mr. Joshua Alder, of Newcastle-upon- 

 Tyne, for frequent contributions of British species. The 

 late Professor Bailey, of New York, kindly supplied me 

 with specimens of Spongilla from North America. To 

 Mr. H. W. Bates I am indebted for my knowledge of some 

 of the most interesting species of the Spongillidae of the 

 river Amazon ; and Mr. J. Spence Bate I have to thank 

 for the loan of many interesting species of British sponges. 

 To my late friend, Mr. G. Barlee, I am deeply indebted 

 for repeated collections of British species of sponges from 



