134 



Part III. — Twenty-third Annual Report 



(8) 10-Scm. — Two zones quite distinct. 



(9) 13'2em. — Shows three zones. 



FEMALES, IMMATURE. 



(1) S'Ocm. in length. — Only central area present. 



(2) 9'2cm. in length. — Otolith shows two distinct zones, the external 

 one being defined by a sharp boundary line, and commencing with 

 several laminae of very opaque deposit (fig. 8, pi. vii.). 



(3) lO'Scm. in length. — Two zones visible, the central area small and 

 not quite so sharply defined as usual — 12 - 0cm. 



(4) 15 ''5cm. in length. — Two zones rather less distinct than usual, 

 central area showing distinct lamination. 



(5) 15'9cm. — Shows three distinct zones. 



According to these results, therefore, males from 6*6cm. to 9 , 8cm. in 

 length are one year old, and at 10'5cm.. or 4-i- inches, are two years old, 

 Females may be one year old up to 8'9cm., or very nearly 4 inches, 

 while others from 9'2cm. to 15*5cm., or 4 to 6 inches, are two years 

 old, and one of 15 9cm., or about 6| inches, is three years old. 



According to Heincke, in the Report of the International Committee, 

 vol, iii., the plaice at the Sylt are from 10cm. or less to 14cm. at one 

 year of age, 10cm. to 19cm. at two years, and 13cm. to 28cm. at three 

 years. These sizes are taken from specimens collected in March, and 

 therefore comparable with those from the Solway Firth examined by me. 

 The results therefore agree, but Heincke's observations have the defect 

 that males and females are not distinguished in them. 



Specimens of Plaice received from Aberdeen on May 8, 1905, 

 and caught a few days before. 



These specimens, of which 14 were carefully examined, ranged in length 

 from 4"8cm. to ll*4cm., and only one was identified as a female. The 

 others were either male or their sex could not be determined. They must 

 be considered as belonging to last year's brood, as the young plaice of 

 the current year have but just completed their metamorphosis. 



(1) JyScm, long. — Sex not determined. One zone only in otolith, 

 transparent ring next to the nucleus not seen. One year old. 



(2) J/Scnt. long. — Sex not determined. One zone only in otolith ; but 

 there was a narrow, more transparent zone next to the nucleus, as in 

 Keibisch's description of the first year's growth. One year old. 



(3) 5c. m. long. — Apparently male. One annual zone only in otolith, a 

 broad region of somewhat opaque layers round the central nucleus, more 

 transparent narrower zone at outer edge, that is the transparent region 

 next to the nucleus as described by Reibisch, was not visible. Con- 

 centric single layers distinct in the middle zone. 



(.!/) 5'7cm., probably male. — One zone in otolith. 



(5) 5'7cm., probably male. — One zone in otolith. 



(6) 6- 7 cm. /female. — One zone only. 



(?) 7'2cm. i probably male. — One zone only. 



(8-10). — Three specimens, 8 -5cm. long, apparently male, all showing 

 one zone only. 



(11) 9'6cm. i male. — One zone only. 



(12) 9'8c?n., male. — One zone only. 

 (18) lO'Scm., male. — One zone only. 

 (1.$) 11 '^cm, male, — One zone only. 



