No. 382.] METHODS IN PLANKTOLOGY. 737 
described above. Complicating conditions usually appear at 
every stage. . Naturalists are gradually unraveling these com- 
plications. But the point which is of special importance is 
that very many of these marine animals may furnish econom- 
ical, healthful, and delicious food for man. That this may be 
a never-failing source of food supply for an increasing human 
population, not only must the habits, haunts, and life histories 
of such food animals (fishes, molluscs, crustacea, etc.) be eluci- 
dated, but also their relation to natural phenomena, meteoro- 
logical conditions, currents, etc., and especially to the Plankton, 
upon which they depend more or less immediately for food. 
This necessitates study of the Plankton as the basis of food 
supply for our most important marine food animals. 
The study of the economic aspects of the Plankton and the 
application of the results to cultivation of water areas have dem- 
onstrated that the water responds even more bountifully than 
land areas to cultivation. It is an interesting economic fact 
that less than 15 cubic feet of cultivated water is sufficient 
to support at least the head of a family (and probably a con- 
siderable number of other dependents) of Italians in Tarente, 
while 6 cubic feet do the same in Japan. Numerous experi- 
ments demonstrate that the yield of cultivated water area sur- 
passes in essential food elements that of equal area of cultivated 
. land. Herein lies the great importance of a knowledge of the 
Plankton, the basis of marine life. The Plankton also enters 
as an important and, in certain aspects, as an undesirable ele- 
ment into the question of municipal water supplies, and the 
necessity of healthful and palatable drinking water has stim- 
ulated not a little the study of the quantitative and qualitative 
constitution of the Plankton. 
Since the time (1884) when Hensen entered upon his work 
of counting laboriously the number of organisms in known 
quantities of sea water, for the purpose of ascertaining the 
amount of living matter which exists in given volumes of 
water, and thus furnishing a basis for scientific aquaculture, 
much attention has been given to the methods of Planktology 
and rapid progress has been made. The great desideratum 
€ven now is a rapid, simple method by which data can be 
