ON THE PROGRESS OF SCIENCE. XIII 



able, are of the opinion, that the herring attains to full size and matu- 

 rity in about eighteen months. It is also probable that this fish arrives 

 at its spawning condition in one year, and that the eggs are hatched 

 in, at most, two to three weeks after deposition, and that in six or 

 seven weeks more the young have attained three inches in length. The 

 maties, or fat herring, feed, develop their reproductive organs, and be- 

 come full herrings in about three or four months. The herrings then 

 aggregate in prodigious numbers for about a fortnight in localities 

 favorable for the reception of their ova. Here they lie in tiers, cover- 

 ing square miles of sea bottom, and so close to the ground that the 

 fishermen have to practise a peculiar mode of fishing in order to take 

 them, while every net and line used in the fishing is thickly covered 

 with the adhesive spawn which they are busily engaged in shedding. 

 So intent are the fish on this great necessity of their existence that 

 they are not easily driven from their spawning ground ; but when once 

 their object has been attained, and they have become spent fish, the 

 shoal rapidly disappears, withdrawing in all probability into deep water 

 at no great distance from the coast. There is no positive evidence as 

 to the ultimate fate of the spent herrings ; but there is much to be 

 said in favor of the current belief, that after a sojourn of more or less 

 duration in deep water, they return as maties to the shallows and lochs> 

 there to run through the same changes as before. The commission- 

 ers were unable to gain any information respecting the time which 

 one and the same herring may pass through the cycle. The enemies 

 of this fish are, however, too numerous and active to render it at all 

 likely that the existence of any one fish is prolonged beyond two or 

 three reproductive epochs. Great difference of opinion has been held 

 respecting the spawning season of the herrings. The commissioners' 

 conclusion is, that the herring spawns twice annually, in the spring 

 and in the autumn. It is not, however, at all likely that the same fish 

 spawn twice in the year ; on the contrary, the spring and the autumn 

 shoals are most likely perfectly distinct; and if the herring, as is 

 probable, comes to maturity in a year, the shoals of each spawning 

 season would be the fry of the twelvemonth before. 



The food of the herring consists of Crustacea, varying in size from 

 microscopic dimensions to those of a shrimp, and of small fish, particu- 

 larly sand-eels. 



The commissioners ascribe the remarkable variableness in the 

 annual visits of shoals of herrings to the British coasts to the varying 

 quantity of food of the fish, and to the number and force of the 

 destructive agencies at work. Any circumstance which increases or 



