602 SCIENCE PROGRESS 



The increased light and temperature of the early spring leads 

 to an increased assimilation by the diatoms of the inorganic 

 materials which have been accumulating during the relatively 

 cold and dark months of the winter. Under the lowered tem- 

 perature of the winter bacterial activity has been reduced in 

 the sea, and as a result the inorganic compounds of nitrogen 

 on which the diatoms feed have been increasing. More intense 

 sunlight leads to increased assimilation by the chlorophyll these 

 organisms contain. A luxuriance of diatom life results in the 

 sea during the months of February to April, and this has an 

 indirect influence on the general fauna of the sea. The ultimate 

 food matter in the sea is these inorganic compounds of nitrogen, 

 but only the marine plants, and a few forms of animal life, 

 can assimilate such materials. Upon these organisms, upon 

 the diatoms practically, the whole of the animal life in the 

 sea must ultimately depend. Small animals, and whole groups 

 of others, feed chiefly on these lowly organised plants, and 

 are themselves preyed upon by other forms of life. Thus 

 the sedentary mollusca living at the sea bottom live almost 

 entirely on diatoms, and microscopic animals like foraminifera 

 and radiolaria, and in their turn these mollusca form the food 

 of fishes like the plaice. It is evident that the abundance of 

 fishes like the plaice may be conditioned by changes in the 

 sea which lead to a more or less luxuriant growth of diatom 

 life. 



Thoroughly to demonstrate the connection between the 

 physical phenomena taking place in the sea and the abundance 

 of useful animals therein requires the study of hydrographic 

 events on the one hand, and of fishery statistics on the other. 

 It is only by the consideration of the catches made by the 

 fishing fleets that we can form really useful estimates of the 

 varying abundance of fishes on the various grounds ; and it 

 is also by observations of the movements of the fishing vessels 

 from ground to ground in pursuit of the fish shoals that we 

 can properly follow the migrations of the latter. Both these 

 lines of investigation are necessary if we wish to establish 

 thoroughly the causes of the migrations of the fishes, or deter- 

 mine what are the factors which operate in producing local 

 abundance or scarcity in particular fisheries. These are pre- 

 eminently the kinds of investigations for which an international 

 organisation is necessary. It is quite impossible that the 



