INTRODUCTION 



it is self-evident that the common work of marine investigation, in which the North- 

 European nations have joined, must take its commencement from what we already know con- 

 cerning the sea and the life of the sea. From the beginning therefore, the investigations have 

 been so instituted as to use and further the methods and results which existing institutions 

 have already worked out in this field of enquiry. The international work is so closely bound 

 to these results that it is often impossible, in the following review of the later work of tlie 

 last two years, to show what comes from the present and what from the earlier investigations ; 

 moreover, it was to some extent the same naturalists who conducted the work formerly as at 

 present. We have thought it better accordingly, for the sake of continuity and the deeper inter- 

 relations of the work, to keep chiefly to the facts and we have laid less weight on what both 

 series of investigations have obtained separately. We would point out however, that the 

 historical development is such, that the new and extended international investigations are 

 in all essentials based on the results achieved by the earlier; tlie aim of both is the same and 

 the means are of the same kind, but tlie new means regarded from the purely quantitative 

 standpoint are greater. We have every reason to expect that the results will likewise be greater. 



The following report will perhaps confirm this view even though all the material is far 

 from having been worked out. 



I. GEOGRAPHICAL DISTRIBUTION OF FISHES 



The region witliin whicli the international investigations are being pursued, offers in its 

 various parts the most varied physical conditions for the life of fishes and the practical fisliing 

 industry. Thus, experience has shown above all that depth, temperature and salinity, have the 

 greatest influence on the occurrence of the various species of fishes and on tlie richness of 

 the animal life. 



It follows therefore, that the first preliminary condition of all fisheries investigations, whether 

 practical or theoretical, must be an exact and purely geographical knowledge of the various 

 parts of the ocean, and that only on such a basis, can wider plans be built for tlie detailed 

 study of tlie natural history and migrations of tlie various species. 



I* 



