402 Professor W. C. Mcintosh [Feb. 1, 



deeper water. Such would not, however, seem to be the case with 

 certain skate, very large adults of which occur in the shallow water 

 of the sandy voes in Shetland. 



On the other hand the witch {Pleuronectes cynoglossus) keeps to its 

 special areas, both as regards the young and the adult condition, so 

 that the movements of eggs, larval and post-larval forms, are circum- 

 scribed ; and the same would seem to be the case with the topknot 

 ( Zeugojyierus) and sail-fluke {Arnoglossus). The dab [Pleuronectes 

 limcmda), again, is found in all stages both in comparatively deep 

 and in comparatively shallow water. 



Almost all our valuable food-fishes, therefore, are produced from 

 minute pelagic eggs, the enormous numbers of which provide for a 

 vast increase and wide distribution of the species ; yet it cannot be 

 said that this habit alone provides for their multij)lication when the 

 case of the herring with its demersal eggs, fixed firmly to the bottom, 

 is considered. It has to be borne in mind, however, that the larval 

 herring immediately mounts upward toward the surface as soon as 

 its strength suffices. 



Many striking changes occur during growth, both in external 

 form and coloration, but it is difficult at present to lay down any 

 general law that would apply to all cases, though those in which 

 certain migrations take place during growth show such changes very 

 prominently. The young round fishes by-and-by roam about the 

 sea in shoals, led hither and thither mainly by the presence of food ; 

 though in the case of the larger and adult forms, safety or freedom 

 from molestation may have some influence. Though so minute on 

 escaj)ing from the egg, their growth is, by-and-by, rapid, and the 

 duration of life in such as the cod is considerable. Abundance of 

 food, more than any special instinct, would appear to be the main 

 cause of their migrations in the adult or semi-adult state, and that 

 food is as varied as their haunts ; in short it embraces every sub- 

 kingdom up to their own, for fishes and their eggs form a large share 

 of their diet. 



There would be little difficulty in adding to the sea great numbers 

 of larval forms of any species of which eggs can be procured : yet if a 

 few adults can be obtained in such waters at the proper season it is 

 still an open question whether the natural process with its surround- 

 ings would not be more successful. 



In the foregoing remarks I have but touched on a few of the 

 leading features of the life-history of a food-fish ; for the subject is 

 one of vast extent, and some of the points embraced in it are by no 

 means easily solved. We have only earnestly entered on the study 

 of the subject in this country within the last few years, and much yet 

 remains to be done, even in some of the most common marine fishes. 

 However, the zoological investigator is here stimulated by the fact 

 that all his labours directly bear on the public welfare, for it need 

 hardly be pointed out that a thorough knowledge of the development 

 and life-histories of our food-fishes is the first step to sound legisla- 



