SEA-FISHERIES LABORATORY. 147 



It lives, too, permanently on the sea bottom, often buried 

 in the sand, feeds almost exclusively on bivalve molluscs, 

 and in body form departs widely from that usual in fishes. 

 On the other hand, the Cod is an active fish, which may 

 migrate over wide sea areas, and although it affects the 

 bottom, it may be found in any vertical zone of the sea. 

 Further, it is voracious and even cannibalistic, and, 

 although it feeds mostly on Crustacea, many marine 

 groups of animals contribute to its food, whilst it has the 

 typical piscine form. Nevertheless, we shall show that 

 the morphological differences between the two fishes, apart 

 from the question of symmetry, are comparatively few 

 and unimportant. 



The following parasites of the Plaice have come under 

 our own observation: — (1) Unidentified Sporozoan cysts 

 imbedded in the wall of the gut, and reducing it to a thin 

 membrane ; (2) unidentified Myxosporidian cysts within 

 the cartilage of the auditory capsule, and causing a con- 

 siderable hypertrophy of the same ; (3) the Cyclops stage 

 of Lerncea, attached to the gill filaments ; (4) Chondra- 

 canthus cornutus, inside the gill cover ; (5) Lepeophtheirus 

 2'jectoralis, on the skin under the pectoral and pelvic fins ; 

 and ((')) Bomolochus sohce in the nasal chamber. There are 

 of course others, but these we have seen. 



Only seven genera and fourteen species of 

 Pleuronectidse are known to inhabit British seas. The 

 members of the genus PI euronectes are P. platessa (plaice), 

 P. limanda (dab), P. flesus (flounder), P. cynoglossus 

 (witch), and P. microcej^halus (lemon sole). All these 

 species are known in the Irish Sea area. The Plaice is 

 probably the most abundant, and the order of the species 

 in the above list gives the relative abundance of the others. 

 All are important edible fishes, and are the objects of an 

 active fishing industry. 



