THE COD FAMILY. 243 



grey forms feeding in sandy spots on annelids and young Cotti. 

 Similar stages are abundant on our own shores. In February 

 or approximately one year from hatching, the codlings are about 

 1 foot long, and during the second year they migrate seawards 

 to return in their third or fourth year as full-grown cod, a 

 second migration further seawards taking place at the time of 

 spawning. The cod does not appear to be mature till the third 

 year. The rate of growth seems to be exceptionally rapid, a 

 medium-sized codling being capable of adding 6 or 7 inches to 

 its length in the course of a single year. 



The subject of the rate of growth of fishes, although very 

 important is still in an uncertain state and further data are 

 needed. It is more than probable that the size attained by a 

 fish before sexual maturity varies within wide limits and is 

 largely determined by the nature and quantity of food, and by 

 environmental factors. 



Hence experiments with fishes growing under artificial con- 

 ditions must not be allowed to have too much weight, although 

 their value is increased the more closely the natural conditions 

 are imitated. 



Dannevig 1 succeeded in rearing a number of young cod in a 

 large confined basin with a capacity of 2500 cubic metres, and 

 noted carefully the growth in length. The following table, 

 corrected to inches, is taken from his paper : 



Date. Age. 



April 26 Hatched 

 May 3 6 days 



16 19 



18 21 



21 24 



31 1 month 5 



June 3 1 ,, 8 



>* 



,,6 1 11 





 ) 



July 12 2 15 



August 12 3 15 



Sept. 12 4 15 



Oct. 12 5 15 



1 See abstract of Dannevig's Report by Walter Webster, Scottish F. B. 

 Report, 1886. 



162 



