34 LIFE-HISTORY AND DEVELOPMENT OF 



by the help of the Trawling Commission under Lord Dalhousie, 

 and subsequently by the aid of the Fishery Board. It may be 

 asked, Why is all this remarkable variation in colour ? Just for 

 the same reason that the young tapirs and wild pigs are striped, 

 or the young red deer spotted — the adults in each case being 

 uniformly tinted. Such features indicate their genetic relation 

 with ancestral forms having these marks ; and, moreover, in the 

 struggle for existence such variations in tint conduce to the 

 safety of the young. 



The view of Eimer that the markings in animals are 

 primitively longitudinal would not suit for many fishes, notably 

 for the young cod, ling, and Pleuronectids, and, indeed, Haacke 

 has already pointed this out from a study of the Australian 

 fish, Helotes scotus'^, the adult of which is marked by eight 

 longitudinal bands, while young specimens present in addition 

 a row of clear transverse bands which subsequently disappear. 



The larval salmon enters the world of a size — though small — 

 that is readily recognisable, viz., about three-fourths of an inch 

 in length, but the marine forms under consideration, from their 

 minute size and glassy translucency, are almost invisible to the 

 naked eye — ^just a gleam of light broken by the passage of 

 a different medium, or a tinge of pigment, arresting attention. 

 Only in the wolf-fish or cat-fish (which is not much — though it 

 ought to be more — of a food-fish) with its large egg, have we a 

 size nearly reaching that of the salroon at birth. 



We had left the larval fish tossed about by the currents and 

 unable to struggle against them, now 

 floating with its yolk-sac uppermost, 

 or hanging in the water with its head 

 downward, and again making spasmodic 

 darts hither and thither. Soon, how- 

 ever, it gathers strength, and at the 

 end of a week or ten days it glides 



actively through the water, and avoids 



T ^T T ^ T ^ ■ , Pig- 10. Anterior (ventral) 



both obstacles and enemies, the young region of larval Cod with 



cod nimbly escaping the forceps, poising great breast-fins. Mag- 



I One of the Pristipomatidas. 



