8 



REPORT ON THE PRESENT STATE OF KNOWLEDGE 



The rate of growth required to meet the views of the different 

 observers is approximately represented in the following table : — 



Two columns are added showing the rate of growth of the cod, as 

 determined by Dannevig from specimens reared in a large pond, and of 

 the herring, as determined by Meyer for the river Schlei, the observa- 

 tions in the latter case being confirmed by the rate of growth of larvae, 

 which Meyer succeeded in rearing in confinement.* 



It will be seen that the rate of growth suggested by Cunningham is 

 much slower than that regarded as probable by the other observers. He 

 considers the fish from 16 to 2L cm., which are taken in November, as 

 being derived from the spawning of the previous year, being therefore 

 16 months old. At the same time he regards the mackerel, 22 to 23 cm. 

 long in June, as only one year old, and explains the difference as due to 

 the great individual variation in growth rate. 



There are no doubt great difficulties in the way of accepting the very 

 rapid growth suggested by the French and American observers, and by 

 Mr. Dunn. If their view is correct, the rate of growth of the mackerel 

 will be much more rapid than that of the herring, approaching more 

 nearly that of the cod reared by Dannevig, The question is, however, 

 one which can only be settled by further research. 



Size and Maturity. — With regard to the size at which the mackerel 

 begins to breed, practically nothing is known. Marion states! that 

 the fish which are 20-24 cm. (9 inches) long in February, and r>hich 

 he regards as one year old, have the reproductive organs well advanced. 



* Soe Cunningham. Journ. Mar. Biol. Assoc., N.S., vol. ii. pp. 223 and 236. 

 t Ann. Mus. Nat. Hist. Marseille Zool. AppUquic, i., 1889, p. 87. 



