288 



Maturity. 



The condition of the testes was not ascertained in any of the males recaptured ; 

 the condition of the ovaries of 3 of the females was recorded. One, taken in 

 October 1913, 20 miles to the north and east, was " nearly ripe " ; the others were 

 " immature." 



EXPERIMENT IX. 



21th March 1913. 



On the same day, 72 plaice, consisting of 22 males, 48 females, and 2 of un- 

 known sex, were hberated at 58° 10' N. ; 2° 30' W. They were part of the lot taken 

 in the Firth of Forth on the previous day. The males measured from 29*5 to 37 "5 

 cm., and 9 were under adult size on Hberation ; the females measured from 31 to 43 

 cm., and 31 were under adult size on liberation 



The numbers liberated and recaptured, arranged in 5-cm. groups, are as 

 follows : — 



cm. cm. cm. cm. 



2.5-30-5 .31-35-5 36-40-5 41-45-5 Total. 



F. Lib. ... — 24 19 5 48 



F. Recap. . . — 10 12 4 26 



M. Lib. . . 2 16 4 — 22 



M. Recap. . . 1 8 2 — 11 



?Lib. ... — 2 — — 2 



? Recap. . . — — — — 



The number recaptured was 37, or 51-4 per cent., 11 males (50 per cent.) and 

 26 females (54-2 per cent.). All the males w^ere of adult size when recaptured, 

 measuring from 34 to 42-5 cm., and averaging 36-3 cm., as compared with a range 

 of from 29-5 to 37-5 cm., and an average of 33-5 cm. on liberation ; they were at 

 liberty for from 24 to 485 days, the mean being 199 days ; they travelled from 13 to 

 39 miles, the average being 23-5 miles, and the mean rate 1-1 miles. Twenty of 

 the females were of adult size, averaging 43-5 cm., and ranging from 38-7 to 51 -3 cm., 

 as against a range of from 32-5 to 43 cm., and an average of 38-2 cm. on hberation ; 

 they were free for from 6 to 1098 days, the average being 310 days ; they migrated 

 from 7 to 69 miles, the mean being 25-7 miles, and the mean rate -8 mile. Six of 

 the females were under adult size, the average being 34 cm., as compared with 

 34*2 cm. on liberation ; they were at hberty for a mean period of 30 days, and 

 travelled from 13 to 45 miles, the mean being 19-3 miles, and the mean rate 6*3 

 miles. 



The Extent and Direction of Migration. 



First Quarter. — One male and 6 females were recaptured in April ; the position 

 of the male was recorded merely as " Moray Firth " ; all the females were taken 

 to the north and west, at distances of from 10| to 19 miles, mostly towards Cl}^h 

 Ness, or Berriedale Ness. 



Two males and 3 females were recaptured in May, 1 male 14 miles to the north 

 and west, and the other 30 miles to the south and west, near Buckie ; 2 of the 

 females were taken to the north and east, at 13 and 14 miles, south-east of Noss 

 Head ; and the third was caught in Burghead Bay, 45 miles to the south and west. 



None was taken in June, so that the total recaptures in the first quarter were 

 12, or 32-4 per cent., the place of capture being known for 11, or 29-7 per cent. ; 

 of those, 7 were taken to the north and west, and 2 each to the north and east and 

 south and west. 



Second Quarter. — In July, a female was taken near Noss Head, 24 miles to the 

 north and west, and in August 2 females at 7 and 9 miles to the north and east. 



Two males and a female were taken in September, the place of capture of the 

 female being somewhat uncertain, but it was landed at Cromarty, in the Moray 

 Firth ; the males were taken together, 14 miles to the north and west, south-east 

 of Clyth Ness. 



