130 



Part III. — Tiventy-third Annual Report 



In the coracoid four complete zones are visible, and an outer fifth, 

 which is narrower. In the sub- and inter -operculum I can make out 

 no distinct zones or boundary lines. 



(Jf) 50cm. (about 1 ft. 8 in.) mature, with ripe ovaries. — In the 

 right otolith six complete zones visible and a peripheral seventh. I was 

 in some doubt whether this last was the seventh annual growth in pro- 

 gress, or whether it was really complete in the preceding winter and the 

 eighth about to commence The latter view seems more probable, so 

 that this fish is seven years old. As it is far beyond the limit of size 

 for immature plaice, it may have spawned either once or several times 

 previously. 



The zones in the scales were rather difficult to distinguish, but there 

 were apparently seven, including the central region and the extreme 

 external zone. In the coracoid also there were visible six complete zones 

 and a seventh at the periphery. The latter was narrower than the 

 others, and opaque, like the commencement of a year's growth. At present 

 I do not know when the new growth commences, but in examining other 

 specimens subsequently I have assumed that the outermost zone in 

 specimens collected in March and April represents the last complete 

 year, and not the commencement of the new annual growth. 



Heads and Pectoral Regions of Plaice sent from Aberdeen, 16th 

 December 1904 : Sex not [stated. 



(/)' 26'2cm. (10k inches actual measurement). — Otolith shows three 

 zones, that is to say central area, complete second zone, and external 

 zone. The fish is therefore in its third year ; the third year would be 

 completed some time in the commencement of next year. 



(2) 31' 2cm. (12k inches actual measurement). — Otolith shows same 

 condition, indicating that the fish is in its third year. If I understand 

 him aright, this would be placed by Heincke in the second group, plaice 

 which have lived two complete years and are in their third. In this 

 case, the fish is larger than the maximum for this age of plaice on the 

 Sylt grounds off the German coast (fig. 12). 



(3) 35cm. (14 inches actual measurement). — Otolith shows four com- 

 plete zones, and a fifth at the margin. Same number could be made out 

 in the scales, in the coracoid, and in the conical hollow on the faces of the 

 vertebra? (pi. viii., fig. 11 otolith, fig. 10 scale). 



(4) S7'Scm. {15 inches actual measurement). — The otolith shows 

 seven zones, including both the central area and peripheral zone. Accord- 

 ing to this, the fish was in its seventh year (pi. vii., fig. 5). The first three 

 zones are strongly separated, but the fourth and sixth boundary lines were 

 much less distinct, and it seemed possible that they might be accidental 

 and not annual lines. In this case, however, the fourth and fifth zones 

 would be of disproportionate width, so that it seems more probable that 

 the fish is really in its seventh year and not in its fifth. 



(5) 46 '8cm. (18\ inches actual measurement). — The otolith shows 

 five fcones, including the peripheral one. In this specimen I examined 

 the hollow of the vertebral centra and the coracoid, and have figured 

 them (fig. 14). In these also five zones can be distinguished, though the 

 central area of the vertebral surface is scarcely visible, that is to say it is 

 difficult to make out its boundary line. 



I also examined a large plaice 50 5cm. long, bought at a fishmonger's 

 in London last autumn. The otolith showed six zones. The fish was a 

 mature female, and was therefore in its sixth year. 



