PLANKTONIC STUDIES. 609 
and uniform plankton when this exceeds three-fourths and forms almost 
the whole mass. 
In general the mixed plankton is more abundant than the simple, 
since as a rule the circumstances of the “struggle for existence” condi- 
tion and vary in many ways the constitution of the planktonic flora and 
fauna. Still there are numerous exceptions to this rule, and at many 
points in the ocean (especially in the zodcurreuts) there occurs locally 
a development so numerous, and an accumulation of a single form or 
group of forms in such swarms, that these in the haul of the pelagic net 
form more than one-half the entire volume. This monotonic plankton 
appears in very different definite forms; for the difference of climate, 
the season, the oceanic currents, the neritic relation, etc., determine 
significant differences in the quantitative development of the plankton 
organisms, which simultaneously appear in vast numbers ina definite 
region. I will next briefly go over the single forms of the monotonic 
plankton known to me, passing over, however, the consideration of the 
extremely manifold composition of the polymixie plankton, since I am 
reserving that as well as a contribution of a number of mixture-tables 
for a later work. 
1. Monotonic Protophytic Plankton.—Of the seven groups of pelagic 
Protophytes, at least three, the Diatoms, Murracytes, and Peridinea, 
appear in such quantities in the ocean that they alone may constitute 
the larger part of the collection of the pelagic nets. The most impor- 
tant and most common is the monotonic diatom-plankton, particularly in 
brackishand coast waters. The siliceous-shelled unicellular Protophytes 
which compose this belong, often predominantly or almost entirely, to 
a single species or genus, as Synedre in the colder, Chetoceros in the 
warmer seas. The colossal masses of Arctic and Antarctic diatoms, 
which form the *black-water,” the feeding-ground of whales, have been 
mentioned above. In the warmer tropical and subtropical parts of 
the ocean such accumulations of diatoms seldom ornever occur. Here 
their place is taken by the monotonie murracyte-plankton, composed of 
immense swarms of nyctipelagic Pyrocystide. Less frequent is the 
monotonic peridinee-plankton. Although these Dinoflagellata take a 
very significant part in the composition, especially of the neritic plank- 
ton, yet they do not often occur in such quantities as to form the 
greater part of the volume of the capture. 
2. Monotonic Metaphytic-Plankton.—Among the pelagic Metaphytes 
there are only two forms, the Oscillatorie and the Sargassec, which 
appear so numerously that they form the greater part of the pelagic 
tow-stuff. The monotonic oscillatoria-plankton, as a rule formed of 
Swimming bundles of fibers of a single species of Trichodesmium, ap- 
pears in many regions of the tropical ocean in such masses that the 
quantity of the pelagie fauna is diminished on that account. The 
monotonic sargassum-plankton, formed of “swimming banks” of a single 
fucoid, Sargassum bacciferum, is the characteristic massive form of 
organic life in the Halistasa of the “Sargasso Sea.” 
H. Mis. 113——39 
