251 



JaJiuary 1916, after 943 days, near Aberdeen Bank, 50 miles to the north and wesr. 

 The others were " immature." including one measuring 39-5-iO-7 cm., caught on 

 29th April 1914. 



Females. — The condition of the ovaries were ascertained in 12 of the 15 recap- 

 tured. None was " spawning " or " ripe," but three were described as " spent." 

 One, of 43'5-47 cm., was taken at Aberdeen Bank, at a distance of 59 miles to the 

 north and west, in April 1914 ; anotlier. of 40.5-41 cm., was taken in the Moray 

 Firth, off Banff, at a distance of 122 miles, on the 1st ,\pril 1914 ; the third, which 

 was much under tne adult size, measuring 28-5-30 cm., was described as "spent," 

 doubtless by mistake. The other females were " immature." 



Experiment at 220 Miles East of the Isle of May. 

 \m June 1913. 



At this position, which lies in Lat. 57° 15' N. ; Long. 3° 54' E., near the Great 

 Fisher Bank, 106 marked plaice v/ere liberated on 16th Jmie 1913, in a depth of 37 

 fathoms. Fifty of the fish were males, the sizes ranging from 26-5-48 cm., and 

 19 were under the adult size. Fifty-five were females, ranging in size from 26-57 

 cm., 39 bei.ng under the adult size. There was only 1 fish whose sex was not 

 determiiied. 



As no record exists on the subject, there is some doubt as to the place where 

 the fish used in this experiment were captured, but, as the vessel had been trawl- 

 ing in the neighbourhood on that day and the day before, it is probable they were 

 obtained locally. 



The numbers hberated and recaptured, arranged in groups of 5 cm., are shown 

 in the following table : — 



Only 17 of the marked plaice, or 16 per cent., were recaptured, namely, 8 males 

 (16 per cent.) and 9 females (16-4 per cent.). 



Seven of the males were of adult size on recapture, ranging from 35-7-40-3 cm., 

 and averaging 38*1 cm., as compared with a range of from 32-5-37 cm., and an 

 average of 35 cm. on liberation ; they weie at Uberty for from 80 to 397 davs, the 

 mean being 207 days ; the dista^ices migrated were from 15 to 53-5 miles, the 

 average being 32-1 miles, and the mean rate 1-8 miles. 



Six of the females were of adult size on recovery, ranging from 38*2-45-3 cm., 

 and averaging 41-6 cm., as compared with a variation of 34-45 cm., and a mean of 

 38-2 cm., on liberation ; they were at liberty for from 72 to 440 days , the mean 

 being 227 days ; the distances migrated vaiied from 8 to 228 miles, the average 

 being 92-6 miles, and the mean rate, per 10 days, 4-1 miles. Three of the females 

 were under the adult size on recapture, the average being 35 cm., compared with 

 33*6 cm., on hberation ; they were free for an average period of 59 days, and 

 migrated a mean distance of 25*2 miles, at a mean rate of 4*2 miles. 



The Extent and Direction of Migration. 



The fish in this experimert moved in various directions, so that the lines of 

 movement, as represented on the chart, are stellate. 



First Quarter. — A female, of 32-31 "9 cm., was taken in Ju.ly, after 15 days, 32 J- 

 miles to the eastwards (S. 82° E.) In August, 2 females were recaptured, both 



