378 THE FLOUNDER FAMILY. 



the dab than in the plaice, the height of the body is relatively 

 greater in the plaice than in the dab, and the size of the eye, 

 as compared with that of the head, is larger in the dab than 

 in the plaice. Moreover, a general pigmentation of the ocular 

 side is assumed by the young plaice at a smaller size than in 

 the case of the young dab." 



Fig. 6, PI. XVI, represents a dab of a length of 12'25 mm. 

 or about the same length as Plate XV, fig. 3, of a young 

 plaice, so that the general appearance of the two may be easily 

 compared. One of the most marked characters is the forward 

 extension of the dorsal fin on to the head in the plaice and the 

 absence of this in the dab, so that there is a gap in the latter 

 between the dorsal fin and the eyes. This and other features 

 point to the fact that the dab, although a smaller fish, takes a 

 longer time, or at least attains a greater size, before completing 

 metamorphosis. The young dab here figured and referred to is 

 in its structural characters at nearly the same stage as that of 

 the 10 mm. plaice, Plate XV, fig. 2. We may note that the 

 general arrangement of the black pigment closely resembles 

 that described for the plaice, and the gradual increase of 

 the same is noticed, the dorsal and anal fin-rays being later 

 marked out with black spots. The characteristic pleuronectid 

 succession of dorsal, anal and caudal bars or patches may be 

 noticed. 



In Plate XVI, fig. 7, is shown a later stage at 15'25 mm. 

 in length. Here the brownish pigment has appeared and 

 shows the same tendency as in the plaice to aggregate into 

 patches which are also partly arranged in transverse bands 

 corresponding to those of the black pigment-patches. A little 

 later than this, the brown pigment no doubt becomes diffuse 

 as in the plaice. 



In the young plaice, the brown pigment first appeared at 

 a length of about 12'87 mm. (Plate XV, fig. 3), and such a 

 form is in other features at about the same stage as that of 

 the young dab under consideration. 



An observation of Petersen's is not without interest here. 

 He remarks " while the pelagic stage of the plaice in our seas 

 is generally ended with a length of lO'll mm., that of the 



