148 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



A.— EXTERNAL CHARACTERS. 



The Plaice is not a large fish compared with many 

 edible fishes, and the largest of which we find a record 

 was 33 inches long, 21 inches high, and weighed 151bs.t 

 An average large plaice, however, wonld have an extreme 

 measurement of 24 inches long and 14 high. The com- 

 pression of the body is not from above downwards, as in 

 the skate, but from side to side, so that when the fish is 

 lying on the sea bottom its left side is downwards and the 

 right only is exposed. For the sake of convenience, and 

 for obvious reasons, we shall follow Traquair in referring to 

 the right and left sides as the " ocular " and " eyeless " 

 sides respectively. 



The eyeless side of the Plaice is colourless and flat, 

 whilst the ocular side is pigmented and convex. The 

 colour varies very greatly according to the nature of the 

 sea bottom, and may be anything from grey to dark brown. 

 The characteristic orange red spots (ocelli) form a row of 

 about 6 on the dorsal fin, 15 or so on the body, one on the 

 caudal fin, and another row of about 6 on the anal fin. 

 Specimens with the eyeless side more or less coloured, and 

 also reversed examples, are occasionally met with. The 

 nature of the colouration has been investigated by 

 Pouchet,+ and by Cunningham and MacMunn.* We 

 follow the latter memoir. If a superficial section be made 

 of the fresh unprepared skin of the ocular side, two struc- 

 tures only are apparent. These are the colour cells or 

 chromatophores, situated largely in the dermis, but also 

 found in the epidermis, and the opaque somewhat 

 iridescent reflecting bodies or iridocytes. One layer of 



f Thirteenth Annual Report for 1898 of Inspectors of Sea Fisheries 

 (England and Wales), 1899, p. 10. 



\ Jour, l'anat. phys., 1877, No. 1. -Phil, Trans., 1893, B, p. 765, 



