3 
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 Lernea, attached to the gill filaments; (4) Chondra- 
canthus cornutus, inside the gill cover; (5) Lepeophtherus 
pectoralis, on the skin under the pectoral and pelvic fins ; 
and (6) Bomolochus solew in the nasal chamber. There are 
of course others, but these we have seen. 
Only seven genera and fourteen species of 
Pleuronectide are known to inhabit British seas. The 
members of the genus Plewronectes are P. platessa (plaice), 
P. limanda (dab), P. flesus (flounder), P. cynoglossus 
(witch), and P. microcephalus (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. 
