ROMANCE OF DEPTHS OF THE SEA 113 



at the surface seldom surpass an inch or two 

 in length, have at great depths been taken over 

 two feet long. Again, a remarkable Appendi- 

 cularia, usually quite tiny, attains at great depths 

 five inches in length with a noto-chord as big as 

 a lamprey's. Many of these larger forms are 

 found in the Polar areas, and not only within 

 the Arctic and Antarctic circles do the deep-sea 

 forms surpass their shallow-water relatives in 

 size, but the bottom fauna in these areas is pe- 

 culiarly rich both in the number of species and 

 in the number of specimens. 



Animals which live at the sea-bottom, or on 

 the shore or at moderate depths on the continental 

 shelf, so long as they are embedded in the ooze, 

 or attached to stones or burrowing in the mud, 

 or lying on the ground with feeble or no power 

 of locomotion, are known to students of the sea 

 as BENTHOS. Another category of animals, and a 

 very important one, is the .PLANKTON. The 

 Plankton comprises all animals that drift. They 

 may have organs of locomotion, but their powers 

 of movement are entirely insignificant compared 

 with the currents which sweep them along. Few 

 of the smaller ones, swimming as hard as they 



can, progress more than a few inches a day, and 



H 



