of the Fishery Board for Scotland, 



367 



The hydrographical results of the experiments may be summed up as 

 follows : — 



1. That there is at all seasons a fairly constant slow circulation of the 

 surface water in the North Sea, Atlantic water entering round the 

 north of Scotland and between the Orkneys and Shetlands, and 

 passing southwards along the east coasts of Scotland and England, 

 as far as the neighbourhood of the Wash, then in an E.N.E. 

 direction towards the coast of Denmark, and then northerly along 

 the Danish coast. The surface water may or may not enter the 

 Skagerrak and penetrate to the west coast of Sweden and Norway, 

 according to the prevailing wind. The main body passes up the 

 west coast of Norway and joins the Atlantic stream. The limit 

 between the north-going eastern stream and the south-going 

 western stream varies greatly, probably according to the prevail- 

 ing winds ; as a rule, the extent of the former is greater. 



2. The movement of the surface water in confined areas, like the 

 western part of the Moray Eirth and the Firth of Forth, is irregu- 

 lar, and depends upon variations in the winds and the tides. 



3. That, while the general circulation of the surface water in the North 

 Sea is as above described, the current may be deflected by the 

 wind, or even, under exceptional meteorological conditions, re- 

 versed. 



4. That the speed of the movement is usually about two or three 

 geographical miles a day, but may be much accelerated or retarded 

 by the action of the wind. 



5. That the principal cause of the circulation is probably the influence 

 of the prevailing winds, driving the water towards the eastern 

 side and tending to heap it up there. 



III. — Eelation of the Movement of the Surface Waters to 

 Fisheries. 



The most important object of the experiments from the practical point 

 of view was, as has been already said, to ascertain the carriage by cur- 

 rents of the floating eggs and larvae of the marine food-fishes. With 

 the exception of the herring, of skates and rays, and the catfish, the 

 eggs of the food-fishes are buoyant, and float as tiny, isolated crystalline 

 spheres. The eggs may therefore be wafted considerable distances 

 during the time the embryonic fish is developing within them ; and the 

 distance will depend upon the rate and constancy of the current and the 

 duration of the period of development. Further, when the eggs hatch, 

 the tiny young fishes which escape from them are ill-developed and but 

 poorly endowed with the power of independent movement. They wriggle 

 about by fits and starts, and remain quiescent in the intervals. On 

 emerging from the egg each little fish carries attached to its under sur- 

 face the remains of the yolk, from which it derives its nourishment for 

 a period varying from a few days to upwards of a week, and during this 

 larval stage, at least, it may be said that it is as much subject to be 

 carried by the general movement of the water around it as it was when 

 still within the egg. When the yolk is used up, or a little before it, it 

 begins to feed on the minute organisms in the water, and has then the 

 power of darting for an inch or two hither and thither ; but it is still 

 practically inert so far as its carriage by the current is concerned. It is 

 not, indeed, until some weeks later, when it begins to assume the form 

 of the adult, that it may be regarded as anything like independent of 



