OCEANOGRAPHIC RESEARCHES—GRAVIER, 857 
the north of Europe. Furthermore, the fluctuations in the fisheries 
likewise correspond to the annual variations of the waters of the coast. 
These conclusions, though resulting from five years of intensive study, 
can not yet be regarded as final. Nevertheless, the correlations thus 
far determined permit us to hope that hydrographic researches con- 
ducted methodically and with perseverance will furnish data useful 
to meteorology and to agriculture. 
IV. 
From the beginning the planktonic investigations have been asso- 
ciated with hydrographic work. We have acquired a general idea 
of the distribution of the layers of water in the Norwegian Sea and 
the nature of the principal plankton organisms. The boundaries of 
certain layers of water and of the distribution of certain planktonic 
types have shown an interesting correlation. Enormous collections 
have been made in order to ascertain the changes in the qualitative 
and quantitative composition of the plankton at different seasons; 
and the critical and extended study of this material will lead to the 
preparation of distribution charts, by region and by month, which 
will serve as a basis for our future knowledge. The explorations in 
the North Sea proper, where the conditions are less complex, per- 
mitted us to affirm that there are in the sea definite areas where cer- 
tain species spawn, and that the young stages are carried long dis- 
tances by the play of the currents. It has also been found that the 
presence of masses of the principal plankton species on which the 
fishes feed is correlated with determinable, natural conditions. 
Wherever possible to do so, we have sought to understand the fauna 
of the sea bottom, which has for us more than pure zoogeographic 
interest, for certain kinds of fishes are made up from this fauna. 
Thus, at the Danish biological station, Dr. C. G. Joh. Petersen has 
made some very interesting observations on the bottom animals 
which constitute the food of the plaice, and has drawn from them 
conclusions useful in the plaice fisheries. The work of Appelléf along 
the same lines has led to conclusions pertaiming to the geographical 
distribution of certain animals, and also the physical conditions of 
the earth, as, for example, the very probable subsidence of the Faroe 
Bank to the south of the islands of that name. 
V. 
Among the elements of the plankton the attention of Norwegian 
oceanographers has been especially concentrated on the eggs and 
larvee of fishes. Important discoveries have been made from the very 
first cruise. In the summer of 1900 the Michael Sars found young 
stages (a few centimeters in length) floating hundreds of miles from 
