PLANKTONIC STUDIES. 581 
OCEANIC AND NERITIC* PLANKTON. 
The manifold differences which the character of the plankton shows 
according to its distribution in the sea, lead first, with reference to 
its horizontal extension, to a distinction between oceanic and neritic 
plankton. Oceanic plankton is that of the open ocean, exclusive of the 
swimming bios of the coast. The region of oceanic plankton may from a 
zéological point of view be divided into five great provinces: (1) the Are- 
tic Ocean; (2) the Atlantic; (3) the Indian; (4) the Pacific; (5) the Ant- - 
-arctic. In each of these five great provinces the characteristic genera 
of the plankton are apparent through the different species, even if the 
differences in general are not so significant as in the different provinces 
of the neritic and still more of the littoral fauna. 
The neritic plankton embraces the swimming fauna and flora of the 
coast regions of the continents as well as the archipelagos and islands. 
This is in its composition essentially different from the oceanic plank- 
ton, and is quantitatively as well as qualitatively richer. For along 
the coast there develop, partly under protection of the littoral bios, or 
in genetic relation with it, numerous swimming animal and vegetable 
forms which do not generally occur in the open ocean, or there quickly 
die; but the floating organisms of the latter may be driven by currents 
or storms to the coast and there mingled with the neritic plankton. 
Aside from this the richness of the neritic plankton in genera and 
species is much greater than that of the oceanic. The complicated and 
manifold relations of the latter to the former, as wellas the relations of 
both to the benthos (littoral as well as abyssal), have been but little 
investigated and contain a fund of interesting problems. One could 
designate the neritic plankton also as “littoral plankton” if it were not 
better to limit the conception of the littoral bios to the non-swimming 
organisms of the coast, the vagrant and sessile forms. 
PELAGIC, ZONARY, AND BATHYBIC PLANKTON. 
I keep the original meaning of the pelagic plankton as given forty-five 
years ago by Johannes Miiller, and used since by the great majority 
of authors. Lalso limit the meaning of the pelagic fauna and flora to 
those actively swimining or passively floating animals and plants, which 
are taken swimming at the surface of the sea, no matter whether they 
are found here alone or also ata variable depth below the surface. 
These are the superficial and interzonary organisms of Chun (15, p. 54). 
On the other hand, I distinguish the zonary and bathybic organisms; I 
call zonary plankton those organisms which occur only in zones of defi- 
nite depths of the ocean, and above this (at the surface of the sea) or 
below (at the sea bottom) are only found occasionally, as for example 
many pheodaria and crustacea; also the deep-sea siphonophores dis- 
* Nnpiznc, son of Nereus. 
