156 MARKKTABLE BRITISH MARINE FISHES 



naturalists, nor has the method been applied to many of the 

 British races. Mr. Duncan Matthews made an extensive ex- 

 amination of Scottish herrings, and detailed the results in the 

 Fourth and Fifth Reports of the Scottish Board, and his conclusion 

 was that the German naturalists' results could not be considered 

 as applying to the forms examined in Scotland. But Mr. 

 Matthews does not seem to have applied the German method 

 in such a way as to make a thoroughly sufficient trial of it, and 

 his opinion cannot be regarded as conclusive. 



Putting aside this extremely technical method of examination, 

 we have the certain fact that particular spawning grounds are 

 visited 'once a year regularly at the same season, while other 

 grounds are used at another time of the year. It seems only 

 possible to conclude from this that a particular ground belongs 

 to a particular breed of herrings which uses it from generation 

 to generation, although it happens at times that particular 

 grounds are deserted for a succession of years. Many cases are 

 known where such grounds have been regularly used for a very 

 great number of years. How then can we account for the fish 

 always coming back to their own ground ? This need not be so 

 mysterious as it appears at first sight. Conditions of tempera- 

 ture and food very probably always drive the young fry from a 

 certain ground in one direction, for instance up an estuary. 

 There they remain together and meet with others a year older. 

 The year-old forms when ready to spawn for the first time very 

 probably join the shoals of mature fish when they revisit the 

 same neighbourhood, and so without any marvellous instinct 

 accompany them to the spawning ground which they already 

 know from habit and memory. The case is similar to that of 

 migratory birds ; it is not entirely an incomprehensible intuitive 

 instinct, but a more comprehensible instinct of joining the older 

 flocks ; the simple habit of herding in flocks or shoals is probably 

 the explanation of the whole matter. In order to obtain more 

 certain knowledge about the migration of herrings a great deal 

 of systematic and organised investigation will be necessary. We 

 may safely consider that the old theory which taught that the 

 home of the fish was in the northern seas, and that they annually 

 migrated southwards in one great body at the same time, and 

 that this was the reason why the fishing season was later at 

 southern parts of the cast coast than at the northern, is exploded. 



