DEVELOPMENT AND LIFE-HISTORIES OE TELEOSTEAN FISHES. 791 



The dab (Pleuronectes limanda) has a distribution of pigment similar to that in the 

 flounder, though the yellow spots seem to take a more distinctive linear disposition, two 

 lines running along each side of the embryo, the upper line marking the dorso-lateral limits 

 of the neurochord (PI. V. fig. 11). This distribution is well seen when the embryo is viewed 

 from above. Pigment (yellow) appears when about thirty protovertebrse are outlined 

 (i.e., about the seventh day after fertilisation). On the fourteenth day (two days after 

 emerging) the pigment-spots around the margin of the eyes and the otocysts coalesce to 

 form larger patches, irregular in form. A few days later, the upper lobe of the caudal 

 membrane is diversified by the development of an undulating line of yellow pigment, or 

 rather of a linear series of crescentic patches. Other spots occur thickly in the anal region, 

 but the yellow pigment of the trunk is confined for the most part to two lines, as above 

 described (PI. XVI. fig. 6). In a more advanced embryo, thirteen days after extrusion, 

 the crescentic series of patches in the caudal fin is still more boldly marked, while two or 

 three irregular touches appear on its lower lobe. The stellate pigment-spots are now 

 meagre, occurring, as in the earlier stage just described, over the eyes, along the ventral 

 region, over the greatly diminished yolk-sac, and very sparsely on the tail. The eyes 

 have become darker, by increase of their black choroidal pigment, and about this time 

 they show a striking green lustre in oblique light (PL XVI. fig. 3). 



In the plaice (PI. V. fig. 6) black pigment-spots, mingled with finely stellate 

 bright canary-yellow corpuscles, develop, though comparatively late, and when the embryo 

 is freed it does not show the marked pigmentation of the cod or like forms. On the 

 third or fourth day after emerging yellow pigment appears as very minute amorphous 

 spots. In PI. XVI. fig. 5, the peculiar distribution of the two tints is seen. The head 

 and trunk present very minute, scattered spots. The ventral margin of the alimentary 

 tract shows stellate black spots ; while the upper and lower contours of the caudal region 

 have bold lines of stellate spots, which extend to the caudal fin-membrane, though con- 

 fined to the lower lobe, and here the spots are simple and very minute. The yellow 

 pigment appears only as a narrow area towards the end of the tail, viz., the upper 

 margin of the posterior half of the caudal trunk. At the root of the tail a dense patch 

 of black spots occurs, extending obliquely just above the urinary vesicle. 



Pigment appears in the gurnard at a slightly later stage than in the foregoing forms. 

 It consists of very pale yellow spots, which have a delicate sea-green tinge in certain 

 lights. They are sparsely scattered over the trunk proper, but form a rude line along 

 the dorsum, and an undulating line along the sides and around the eyes. Three or four 

 days later minute black spots occur, and both colours are sparsely distributed over the 

 yolk-sac, and around the large oil-globule. A more advanced embryo is seen in PI. XVI. 

 fig. 8, at which stage irregular patches of yellow and black pigment exist upon the 

 dorsal and ventral portions of the caudal membrane. The spots send out branched 

 ramifying processes, and the pectoral fin exhibits distally a radial yellow and black 

 coloration. The eyes, however, are very slightly tinted with minute black spots. In 

 still later larval and post-larval stages the pigment diminishes, and only occurs very 



