262 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



probably a sufficient number to yield a fair average. In 

 calculating this, however, the total increase has been 

 divided by 29 instead of 27, since two of the fishes have 

 undergone two seasons' growth. One has slightly over 

 one season's growth, but this may be neglected. The 

 average thus obtained is almost exactly three inches. 



This is rather more than the result given by the 

 former table, but it must be remembered that the latter 

 probably under-estimates the rate of growth. If a larger 

 number of marked fishes had been recovered in September- 

 November, the growth would no doubt have been greater. 

 But it is also probable that the results of the second table 

 slightly over-estimate the year's growth. The fishes 

 represented have all been in the sea for over the average 

 length of time between marking and recapture. They 

 are, therefore, probably more vigorous fish than the 

 others, and may have grown more rapidly. Their average 

 initial length was also a little more than the others. 



At any rate the difference is not great, and one may 

 conclude that in the Irish Sea plaice grow about 

 2J inches in the year. This applies to fish which are 

 initially of the ordinary smaller marketable sizes, viz., 

 8 to 10 inches. 



It should be noted, too, that considerable variation in 

 growth rate exists. Thus plaice No. LL19, after a whole 

 season's growth, had increased only J-inch in length. On 

 the other hand plaice No. L152, after a season's growth, 

 had increased in length 5J inches. Both cases are of 

 course extremes, and are quite abnormal. 



The otoliths, or earstones, of about half the marked 

 plaice recovered have been examined, with the object of 

 determining the ages of the fishes. It is well known that 

 the calcareous matter in these structures is laid down 

 regularly, so that every year after the first, two distinct 



