ANIMAL LIFE IN THE SEA"*^ 173 



In the first place it is noticeable that the larger algae 

 are unrepresented in the open sea. The weed which 

 floats at the surface of the Sargasso Sea is an apparent 

 exception, but it is apparent only, for this weed is torn 

 off the shores, especially off the Bahamas, and though 

 it proUferates vegetatively in the open, and can five 

 there for a time, it is not a truly pelagic form. The 

 swarms of animals which live among the floating 

 masses of weed in the Sargasso Sea show what an 

 important addition to the food-supply of the ocean 

 the weed is. 



The basal food-supply of the pelagic animals is, 

 therefore, the phytoplankton, the minute algae which 

 float at the surface. Necessarily these algae, as light- 

 demanding organisms, are limited to the surface layers 

 of the water, being especially abundant in the upper- 

 most 25 fathoms. They occur, though in diminished 

 quantity, down to 50 fathoms. Those found in greater 

 depths are resting stages or dead forms. The dead 

 forms, as we have already suggested, tend to accumu- 

 late, at least temporarily, at levels where a sudden 

 increase of density occurs. As regards quantity, the 

 water of the open ocean seems to be poorer in algae 

 than coastal waters, but, as has been already sug- 

 gested, currents may carry the shore forms out to the 

 ocean, and there's reason to believe that then the fish 

 of the shore may foUow them. 



The next point to be considered is the distribution 

 of pelagic animals. There is a tendency among many 

 writers, at least tacitly, to confine the term * pelagic ' to 

 those forms which live sufficiently near the surface for 

 light to penetrate. There is, however, no real justifica- 

 tion for this use. An animal hving at a depth of 

 2,000 fathoms is as truly pelagic as one hving at 



