1894.] The Origin of Pelagic Life. ; 585 
THE ORIGIN OF PELAGIC LIFE. 
(From Pror. W. K. Brooks.) 
Chapters VII and VIII of Brooks Memoir on Salpa em- 
brace a discusssion of this genus in its relation to the evolution 
of life, and in order to clearly present its position and signifi- 
cance in the economy of nature the author discusses at some 
length the conditions under which oceanic life has been 
evolved. He notes first that the marine animals are almost 
exclusively carnivorous. They prey upon each other to an al- 
most incredible extent, and were it not for the extraordinary 
fertility of pelagic organisms the rapacity of the higher forms 
of life would bring about their own extermination. Mr. 
Brooks, in commenting on the abundance of marine life, in- 
stances the great schools of mackerel, the hunters of herring, 
which in turn swarm like locusts. In 1879, three hundred 
thousand river herring were landed by a single haul of the 
seine in Albemarle Sound; but the herrings feed upon cope- 
pods, each one consuming myriads every day. In spite of 
this destruction and the ravages of armies of medusæ, siphon- 
ophores and pteropods, the fertility of the copepods is so great 
that they are abundant in all parts of the ocean, and not only 
on the surface, for banks of them are sometimes a mile thick. 
On one occasion the Challenger steamed for two days through 
a dense cloud formed of a single species. But upon what do 
the copepods feed? And this brings the author to the impor- 
tant factors in the food supply of the animals of the ocean. 
The basis of all the life in the modern ocean is to be sought 
in the microorganisms of the surface. They consist of a few 
simple unicellular plants, and the globigerinæ and radiolaria 
which feed upon them. These organisms are so abundant 
and so prolific that they meet all demands made upon them. 
They are not only the fundamental food supply, but, accord- 
ing to the author, the primæval supply which has determined 
the whole course of the evolution of marine life. 
