46 
Menge von Nahrung zur Verftigung stehen.« He has constructed an aquarium 
just to study this matter more closely and writes on the results of these experi- 
ments at the same place. The principal production in this aquarium provided 
with bottom plants, in which plankton could not be got to live, was Amphipods, 
which fed on the plants, Fucus vesiculosus and Florideae. The quantity of the Am- 
phipoda became so great, »dass meine Erwartungen in Bezug auf das sich 
entwickelnde Leben in manchen Richtungen ubertroffen worden sind.« 
Hensen has thus shown, that marine animals iu a aquarium can live 
without »plankton«, and even propagate and increase in quantity considerably in 
the course of 2 years. Unfortunately such experiments have certainly rarely or 
never been made since. This shows, that Hensen has known, that the vegetation 
of the coasts may also be of importance, though he only ascribes it a small role 
in the food of the sea; that many of his successors in the study of the plankton 
have so little remembered this, is therefore not due to Hensen. 
In a work published in 1893 by Friedr. Dahl of Kiel, one of Hensen's 
colleagues (Untersuchungen tiber die Thierwelt der Unterelbe. Wissens. Meeres- 
unters. Kiel VI Bericht. 1893), which deals with the bottom-fauna in the mouth 
of the Elbe and contains among other things quantitative determinations of the 
number of animals per m.?, investigated by digging at ebbtide, we find on p. 180: 
»Hensen begann die Untersuchung mit dem Plankton, weil dieses fir die genannten 
Bestimmungen am besten zugånglich schien — —«. »Die Methode ganz allgemein 
auf die am und im Grunde lebenden Organismen auszudehnen, ist bisher noch 
nicht gelungen.« Dahl refers here to quantitative determinations of the organisms 
living together at one place, and he makes these by digging at low-water. 
In the »Deep-Sea Deposits« 1891 of the Challenger Expedition, p. 252, 
John Murray already protested against making the quantities of plankton in the 
sea the sole basis for judging the organic contents of the latter; since large 
quantities are carried out to sea from the land, rivers and from coastal regions. 
C. Apstein in »Das Sisswasserplankton, Kiel 1896« discusses very care- 
fully pp. 102—106 the different sources of the food-stuffs in a freshwater; he also 
recognizes other sources than the plankton. 
K. Brandt (Wiss. Meeresunt. Kiel 1899, Bd. 4, p. 222) mentions, that 
several authors, as Frenzel and Schiemenz, the one for freshwater the other for 
coastal waters, consider the importance of the coastal vegetation for the production 
of animal life as much greater than that of the plankton; but others maintain the 
reverse. Brandt states, that the production of fish-flesh in a carp pond is great 
compared with the product of the fisheries of the North Sea per hectare; but there 
are so many sources of error with regard to the latter, that no great weight can 
be placed upon the statistics. 
On p. 222 Brandt writes: »Wenn man aber den Ocean in seiner Gesamt- 
heit im Auge fasst, so ist unzweifelhaft die Masse und damit die direkte Bedeutung 
der Tange, Seegråser u.s. w. sehr gering, gegeniiber den winzigen Pflanzen des 
freien Wassers.« Brandt is most probably right here. The truth may be that 
in the small fresh and salt waters the coastal plants have as rule the greatest 
importance, but in the large, open seas the plankton, since the bottom-vegetation 
is quite wanting here. All seems to' me to indicate, that the greatest mass of the 
