107 



One was " partly spent " ; it was caught 55 miles to the north and east on 

 19th April 1912. 



Two were " nearly ripe," 1 caught on 12th November 1911, 5 miles to the south 

 and west, and the other on 21st December 1911, 56 miles north and e^nst, off the 

 coast of Aberdeen. 



A male, taken on 30th November 1911, 44 miles north and east, was "about 

 half ripe," and 1 caught on 21st December 1911, 23 miles north and east, off Montrose, 

 was " three-quarters ripe." 



The other 5 adult males, recaptured in the months of June, July, and August, 

 were " immature." Of 4 males under adult size (33 cm.), the condition of the 

 testes in 3 w^as ascertained ; they were all " immature " and were recaptured in 

 July and August 5 and 6 miles to the south and west, \\ithin a short period after 

 liberation, viz. 13, 15, and 56 days respectively. 



Females. — Of the 6 adult females, the condition of the ovaries was ascertained 

 in 4. One, measuring 35-5-43-2 cm., was "about three-quarters ripe" when 

 recaptured on 5th October 1912, 12 miles to the north and east. The others were 

 " immature," and were caught in May, July, and September not far from the 

 station. 



Of 14 females under adult size (38 cm.) on recapture, the condition of the ovaries 

 was ascertained in 12. They were caught in various months, 1 in April, 6 in July, 

 1 in September, 2 in October, 1 in November, and 1 in December. Only 1 had 

 migrated to a moderate distance, viz. 45 miles to the north-east of Aberdeen, in 

 129 days ; it measured 37 cm. in October. The others had moved distances of 

 mostly 5 or 6 miles, and the greatest distance was 19 miles south and west. 



EXPERIMENT V. 



Wth Seftemher 1911. 



The number of fish marked and liberated in this experiment was 105, 49 being 

 males and 56 females. The sizes of the males ranged from 30-5 cm. to 40- cm., and 

 of the females from 27-5 cm. to 44*5 cm. The numbers liberated and recaptured, 

 arranged in 5-cm. groups, are shown in the accompanying table : — 



Five of the males were under adult size (33 cm.) and 39 of the females were under 

 38 cm. 



The fish were taken on the usual ground, viz. Station VI., Firth of Forth (" Fluke 

 Hole "), at 7.40 p.m. on 11th September ; they were marked and ke])t in tanks of 

 running wv.,ter until 11.5 p.m. when they were liberated. None of the plaice died 

 in the interval. 



The number recaptured was 64, or 60-9 per cent, of the total marked, viz. 

 30 males, or 61-2 per cent., and 34 females, or 60-7 per cent. Of the 30 males, 

 29 were of adult size when recaptured ; the sizes before liberation ranged from 33 to 

 40 cm., the average being 36-1 cm., and the sizes on recapture ranged from 34-1 cm. 

 to 44-3 cm., the average being 37*3 cm. ; the period of freedom varied from 7 to 

 640 days, the mean being 196 days ; the distances migrated ranged from 2 to 

 238 miles, the average distance being 53-3 miles, and the average rate of movement 

 was 2-7 miles per 10 days. Of the 34 females, 16 were of adult size when re- 

 captured ; the sizes on liberation varied from 33-5 to 40-5 cm., the average being 

 37-6 cm., and on recapture from 38 to 41-8 cm. the mean being 39-6 cm. ; they 

 were at liberty for from 23 to 439 days, the mean being 181 days ; the distances 

 travelled were from 4 to 81 miles, the mean being 33-5 miles, and the mean rate 

 1-8 miles. Eighteen of the females were under 38 cm. on recapture, their sizes 

 then ranging from 28 to 37-9 cm., and averaging 35-6 cm. ; they were free for from 



