PLANKTONIC STUDIES. | 577 
series of observations for a later and more detailed work. But since, 
to my regret, I am compelled to decidedly contradict the far-reaching 
assertions made by Hensen (22), it is only to justify and prove these 
that I refer to my extended experience of many years. I believe I do 
not err in the assumption that .among living naturalists I am one of 
those who by extensive investigation on the spot have become most 
thoroughly acquainted with the conditions of the plankton and have 
worked deepest into these intricate problems of marine biology. If I 
had not for so many years had these continually in mind, and at each 
“new visit to the sea begun them anew, I would not dareto defend with 
such determination the assertions expressed in the following pages. 
ITI.—_ CHOROLOGICAL TERMINOLOGY. 
The science of the distribution and division of organic life in the sea 
(marine chorology) has in the last decade made astonishing progress. 
Still this new branch of biology stands far behind the closely related 
terrestrial chorology, the topography and geography of land-dwelling 
organisms. We have as yet no single work which treats distinctly 
and comprehensively of the chorology of marine plants and animals in 
a manner similar to Griesbach’s “ Vegetation of the Earth” (1872) for 
the land plants, and Wallace’s “Geographical Distribution of Animals” 
(1876) for the land animals. 
How much there is still to be done is shown by the fact that not one 
of the simplest fundamental conceptions of marine chorology has yet 
been established. For example, the most important conception of one 
subject, that of the pelagic fauna and flora, is now employed in three 
different senses. Originally, and through several decades, this term 
was used only in the sense in which Johannes Miiller used it, for ani- 
mals and plants which are found swimming at the surface of the sea. 
Then the term was extended to all the different animals and plants 
which are found at the surface of fresh-water basins. It was so used, 
for example, by A. Weismann in his lecture upon “the animal life at 
the sea-bottom” (1877), in which he “distinguishes the animal world 
living on the shore from the ‘pelagic or oceanic company living in the 
open sea.’” To a third quite different meaning has the conception of 
the pelagic living world been widened by Chun (1887), who extends it 
from the surface of the ocean down to the greatest depths (15, p. 45). 
In this sense the conception of the pelagic organisms practically agrees 
with the “ plankton” of Hensen. 
Errors have already arisen from the varied use of such a funda- 
mental conception, and it seems necessary to attempt to clear this up, 
and to establish at least the most important fundamental conception 
of marine chorology. In the use of words I will, as far as possible, 
conform to the usage of the better authors. 
H. Mis. 113——37 
