596 SCIENCE PROGRESS 



which does not differ greatly from that of our typical fish, 

 but which, in their adult stages, exhibit quite different habits 

 — that is, they swim about at the surface and at intermediate 

 depths of the sea more or less in shoals. The best examples 

 of this class of pelagic fishes are the herring and the mackerel. 



Again, we may divide fishes into two great categories 

 according to the degree to which they perform migrations. 

 One group, the best example of which is the plaice, may be 

 regarded as semi-sedentary — that is, they do not perform lengthy 

 migrations, but remain through the year on much the same 

 fishing grounds with but little change of habitat. Soles and 

 turbot also belong to this class. The other group contains 

 fishes like the cod and hake, which are notorious wanderers, 

 and visit with more or less regularity the same fishing grounds 

 from year to year at approximately the same seasons. 



It is just this general knowledge of the life histories of the 

 fishes which is of importance to legislators. We require to 

 know where and when the fishes spawn and where the eggs 

 drift to, where the young stages are reared and nourished, 

 what is the nature and extent of the annual migration (if the 

 fish is a conspicuous migrant), how the fishes are distributed 

 according to depth of water, what kind of food they prefer, and 

 generally what are their habits and mode of life. 



Many series of facts of this nature existed before the inter- 

 national research organisation came into existence ; but on 

 reviewing the knowledge of these subjects which is indicated 

 in the literature previous to 1900, it is surprising how many 

 gaps existed. It would be foolish to say that these gaps have 

 been filled up, but the contributions to the subject of the life 

 histories of fishes during the last five years have been numerous 

 and important. The defect of the fishery investigations carried 

 out previous to the beginning of the present century was that 

 the observations of the life history of fishes had mostly been 

 such as were possible with but an imperfect equipment for 

 extended work well out at sea, and, as we now know, with very 

 imperfect fishing apparatus. The great merit of the newer 

 investigations is that they have been prosecuted over wide 

 areas, and simultaneously, by many workers and vessels : parts 

 of the north European seas, which previously had never been 

 adequately investigated, have during the last five years been 

 subjected to a searching analysis of their fish populations. I may 



