282 THE ATLANTIC. [chap. v. 



is unsafe to run the risk of adding to any motion which the 

 dredge may ah-eady have acquired, by attempting to drag it 

 for any distance over the ground. The consequence is, that in 

 those cases where the dredge does reach the bottom, it probably 

 too often sinks at once into the soft ooze and remains clogged 

 with a single " mouthful " until it is hauled up again. Some- 

 times a slight excess of movement in the vessel, from currents 

 or from wind-drift, seems to give a vibratory motion to the 

 enormous length of rope, and to keep the dredge tripping over 

 the ground, so that only a few things are j)icked up by the 

 tangles or clinging to the outside of the net. We must, there- 

 fore, bear in mind that only an infinitesimally small portion 

 of the floor of the ocean at depths over 2500 fathoms has yet 

 been explored. 



Whatever may be the case at the extreme depths referred 

 to, there can be no doubt that at depths which may be regarded 

 as comparatively accessible, say a little above 2000 fathoms, 

 the fauna is sufliciently varied. I give in Appendix B to 

 this chapter a table taken from the Station-book, showing the 

 number of occurrences of representatives of the principal groups 

 of marine animals at the iifty-two stations at which we dredged 

 or trawled successfully at depths greater than 2000 fathoms 

 during the voyage. All the groups marked with an asterisk 

 on this list were represented, having been observed and noted 

 when the trawl or dredge came up. It is very probable that 

 on going over the collection carefully it will be found that 

 many, particularly of the smaller forms, have been omitted. 

 The occurrences of lishes, of cej)halopods, and of decapod crus- 

 taceans must be taken with a reservation ; for it is not always 

 possible to determine whether they were taken on the bottom, 

 or above it during the hauling-in of the net. 



The distribution of life evidently depends in a marked de- 

 gree either upon the nature of the bottom or upon the condi- 

 tions which modify the nature of the bottom. Thus over the 



