THE FLOUNDER FAMILY. 377 



In young plaice and dabs with the eyes in the pelagic 

 condition, that is on each side, the distribution of the black 

 pigment dorsally and ventrally is diagnostic, while the dorsum, 

 in the earlier stages, shows only a limited series of black 

 specks, which at a later stage aggregate into two or three dorsal 

 patches ; the ventral edge is much more boldly pigmeiited 

 with black. A black touch occurs at the angle of the mandible 

 on each side, and, behind, a narrow spear-head of black runs 

 to the clavicular region and ceases. Then a single median 

 line of black extends rather behind the middle of the abdomen, 

 which is speckled with black. Black chromatophores are present 

 at the vent, and a well-marked double series extends to the 

 tail at a later stage also aggregating into the ventral touches. 

 Other marked touches occur along the abdominal roof and on 

 the cheeks. It is a curious feature also that the sides (dorsal 

 and ventral) of the larval tail are mapped out by lines of black 

 chromatophores, e.g. when about 8 '9 mm. in length. While 

 the eyes are silvery in lateral view from the dorsum they are 

 of a fine iridescent green like a diamond beetle's wing. 



The smaller forms of this species and also of plaice and 

 flounders often become the prey of little jelly-fishes (fig. 11, 

 page 56). 



A warm day (e.g. 11 May, 1896) brings the young plaice, 

 dabs and flounders to the surface in numbers apparently after 

 their food, yet their eyes are on the right. They are very trans- 

 lucent, and are about 18 mm. in length. 



Importance is attached to the comparison of these three 

 species in their earliest stages, and to their diagnostic features, 

 because the young fishes after assuming a habitat in sandy and 

 muddy shallows are exceedingly hard to distinguish specifically. 

 In fact, at a certain age it is probable that, in spirit, there 

 is no one feature by which we can with absolute certainty 

 pronounce a given young pleuronectid to be a dab or a 

 plaice. A distinction of approximate value is found in the 

 fact that although a dab, e.g. of \ inch length (Plate XVI, 

 fig. 6), is older than a plaice of the same length, it is 

 thinner and more elongated. Holt states that at the same 

 total length, " the rotation of the eyes is less complete in 



