175 



in the same direction ; the third was caught in December 1913, at 12 miles to the 

 north and east, and the fourth in November 1914, 15 miles to the south and east. 



Among those of adult size (33 cm.), the following, captured during the spawning 

 season, were described as "immature" : — One. of 33-33'3 cm., in February 1914, 

 15 miles to the south and east ; 2 in March 1914, measuring respectively 34-34-7 

 cm., and 33-33"3 cm., 17 miles and 15 miles to the south and east, and 1 taken in 

 April 1914, 12 miles to the south-east, which measured 34-35-2 cm. 



On the other hand, among the males under adult size was 1 described as " ripe," 

 which measured 29-5-29-9 cm., and was taken in February 1914, 20 miles to the 

 south and east. 



Females. — The condition of the ovaries was recorded for 10 of the 11 recaptured. 

 All were described as " immature " (including 1 taken in March 1914, and measuring 

 38-5-38-5 cm.), except the last, caught in December 1916, 67 miles to the north and 

 east, which was described as " ripening." 



Experiments at Aberdeen Bank. 



At this station, which hes about 35 miles to the south-east of Aberdeen, in Lat. 

 56° 55' N. ; Long. 1° 8' W., and where the depth is about 37 fathoms, marked plaice 

 were liberated on eight different occasions, between June 1910 and November 

 1913. The following table gives the main particulars of each experiment : — 



Altogether, 1227 plaice were marked and set free, of which 525 were males, 674 

 were females, and 28 were of undetermined sex. The number recovered was 741, 

 or 60-4 per cent., namely, 305 males (58 per cent.), 429 females (63-6 per cent.), and 

 7 of unknown sex (25 per cent). The percentage of recaptures varied in different 

 cases from 44 to 77. 



EXPERIMENT I. 



10th June 1910. 



In this experiment, the large number of 336 fish were marked and set free, con- 

 sisting of 149 males, 177 females, and 10 whose sexes were not ascertained. The 

 males ranged in size fro-n 20 to 40 cm., and 78 were under the adult size when 

 liberated. The sizes of the females ranged from 23 to 56 cm., and 164 weie under 

 the adult size on liberation. The sizes of those whose sexes were not distinguished 

 varied from 28-5 to 38-5 cm. 



Tlie numbers of the fish marked and recajitured, arranged in 5-cm. groups, aie 

 shown in the following table :— 



