264 RATE OF GROWTH OP SOME SEA FISHES. 



wliicli incline him to modify the opinion expressed in the Eeport 

 proper concerning the age of young fish about 4*5 cm. long^ which 

 already had acquired the permanent form of the adult, and which 

 were taken towards the end of July, 1886. The length of these fish 

 is given in the body of the Report as 3-5 to 3-8 cm. Hoek argues 

 that if the shad {C. alosa) spawns, as Kroyer and Nilsson say, in 

 June and July, these fish must be a year old, and mentions in 

 support of the latter conclusion that the sea-herring takes seven to 

 nine months before it undergoes its metamorphosis from the larval 

 form to that of the adult. This latter fact is taken by Hoek from 

 the results of Meyer and Heincke, published in the Reports of the 

 Commission zur TJ titer suchung der deutschen Meere in Kiel. But 

 it seems to me that, in the first place, Hoek has somewhat exagger- 

 ated the statements of Meyer and Heincke. It is true that the 

 latter observers found that some herring larvae hatched in autumn 

 and winter did not attain to the perfect form until June and July ; 

 but the German investigators do not suggest that the eggs from 

 which these larvae came were shed in October, but later in Novem- 

 ber and December ; and Meyer further points out that the water is 

 then very cold, and that the eggs take many weeks to hatch, so that 

 the larvEe taken in June are more probably four or five months old, 

 reckoning from the time of hatching, than seven to nine months. 

 Another important consideration overlooked by Hoek is that these 

 larvae of the autumn, or sea-herring, are 5 to 6 cm. long before they 

 have completed their metamorphosis, while the young shad to which 

 Hoek refers had already attained to the perfect and permanent 

 form at 4*5 cm. What probability is there that the young of so 

 large a fish as the shad when 4*5 cm. long should be five to seven 

 months older than the larva of a herring 5 to 6 cm. long ? Then 

 again the shad is hatched in spring in warm water, why then 

 should its growth be compared with that of the winter herring, 

 whose eggs and larvae are produced at the coldest time of the year, 

 rather than with the growth of the spring herring ? 



