viii PREFACE. 



circumstances, it has been suggested to me that a 

 small volume, containing, at somewhat greater length, 

 in a more accessible form, and with the advantage 



of illustrations, the conclusions to which I have been 

 v 



led on this interesting subject, might not be alto- 

 gether without interest to the general reader. The 

 result, which has already appeared in the pages of 

 Nature, is now submitted to the public, with some 

 additions. I am well aware that it has no pretence 

 to be in any sense a complete treatise ; that the 

 subject itself is one as to which our knowledge 

 is still very incomplete, and on which the highest 

 authorities are much divided in opinion. Whatever 

 differences of opinion, however, there may be as to 

 the views here put forward, the facts on which they 

 are based will, I believe, be found correct. On 

 this point I speak with the more confidence, on 

 account of the valuable assistance I have received 

 from many friends : to Mr. and Mrs. Busk and Dr. 

 Hooker I am especially indebted. 



The papers above referred to are as follows : 



1. On Labidocera. Annals and Magazine of Natural History, vol. 



xi., 1853. 



2. On Two New Sub-genera of Calanidse. Annals and Magazine of 



Natural History, vol. xii., 1853. 



