2 THE VOYAGE OF H.M.S. CHALLENGEE. 



flicting in some points and harmonious in others. Secondly, because it promises more 

 logically fitting opportunities, whilst discussing the discoveries of other spongiologists, 

 of communicatincf whatever observations of general interest I have made whilst examin- 

 ing the Challenger material, so that the descriptive part of this memoir may be 

 for the most part exclusively devoted to systematic purposes. The following pages 

 accordingly consist of a discussion of the organisation of the Keratosa and of the 

 principles of their classification. 



