PREFACE IX 



water. We may complete our survey of the ocean 

 beds, we may analyse the bottom muds and name 

 and classify the animals that compose their fauna, 

 but there are many things that must remain merely 

 matters of conjecture. We shall never know, for 

 example, with any degree of certainty, how Bathy- 

 pterois uses its long feeler-like pectoral fins, nor 

 the meaning of the fierce armature of Lithodes ferox ; 

 why the deep-sea Crustacea are so uniformly coloured 

 red, or the intensity of the phosphorescent light 

 emitted by the Alcyonaria and Echinoderms. These 

 and many others are and must remain among the 

 mysteries of the abyss. 



Our present-day knowledge of the physical con- 

 ditions of the bottom of the deep sea and the animals 

 that dwell there is by no means inconsiderable. 



It may be found in the reports of the scientific 

 expeditions fitted out by the English, French, Ger- 

 man, Italian, Norwegian, and American Governments, 

 in numerous volumes devoted to this kind of work, 

 and in memoirs and notes scattered through the 

 English and foreign scientific journals. 



It is the object of this little book to bring together 



