1892.] The Problem of Marine Biology. 807 
Currentic Differences. — Conspicuous differences are also 
brought about by the numberless currents, great and small, 
by the little-known deep sea oceanic currents as well as by the 
better-known great surface currents, the Gulf stream, the 
Falkland stream, the Guinea stream and others. These cur- 
rents play a great rôle in the distribution of many forms of 
life. More local influences are exerted by the small currents 
whose causes are found in the climatic and geographical con- 
ditions of the adjacent coast. The relations of Plankton life 
to currents is little known, and needs investigation, but first a 
better knowledge of the currents themselves is necessary. 
Almost everyone who has seen the surface of the ocean in 
a calm has noticed the glassy areas of irregular shape. These 
are found on the high seas as well as in sheltered bays and 
harbors, and are of very special interest to the student of 
marine life. So far as made out they are extremely irregular 
in time and place of appearance, and the conditions govern- 
ing them have not been carefully studied. They are in a 
measure influenced by winds and currents, by the ebb and 
flow of the tide.. Here, into a limited space, are crowded great 
numbers of organic forms; this space is readily distinguished 
from the surrounding water in which there is comparatively 
little life. These phenomena have been noticed by seafaring 
men and have many different names in different countries. 
A word in conclusion as to the bearing and importance of 
the Plankton in human economy in the near future. When 
Malthus promulgated his famous doctrine he failed to con- 
sider the final element which enters into the problem of human 
population, the human mind. The ingenuity of the human 
mind has brought about a decreased efficiency in the natural 
checks to undue increase, and thus an artificial increase in 
the food supply is rendered necessary for the crowding popu- 
lation. This food supply is now mainly derived from the 
cultivation of the land. A still further increase of population 
will necessitate a levy upon marine life. As soon as man to 
any great degree becomes a factor in the Plankton conditions 
by drawing from it large quantities of food, particularly in 
the form of mature animals, the equilibrium of oceanic life 
