326 THE FLOUNDER FAMILY. 



groups of chromatophores became very distinct, viz., one on the 

 body over the middle of the yolk, another at the rectum, two 

 conspicuous bars behind often broken up into a dorsal and 

 a ventral band and a small fifth near the tip of the tail. 

 In the more advanced and more active larva?, with the yolk 

 much diminished, the pigment is more continuous. By re- 

 flected light, the colour of these larval forms is greenish- 

 yellow, and thus it differs from the chrome-yellow of the 

 younger stage. This change of hue appears to be due to the 

 development of the black pigment amongst the yellow. The 

 increase in the size of the pectorals in a few days became 

 marked, and though usually carried more or less obliquely they 

 were fan-shaped when viewed from above. 



The chief changes till the 20th April were the deepening of 

 the marginal fin, both dorsally and ventrally, the extension 

 of the chromatophores both yellow and black of the two 

 conspicuous bars behind the vent into the marginal fin, and 

 the appearance of stellate black pigment-corpuscles along the 

 ventral edge of the fin. Stellate black pigment also occurs 

 on the abdomen, and the eyes are bright silvery. The yellow 

 pigment still forms a line over the medulla and the first part 

 of the cord. The caudal pigment-bar is chiefly black, only 

 two or three yellow specks being present. The pectoral fins 

 are larger and have rays; the upward slant of the mandible 

 and the reduction of the yolk to a small round ball complete 

 the features at this stage. 



After the foregoing stage, in which this species and other 

 pleuronectids resemble the larvae of other fishes in shape, 

 they begin to exhibit an increasing depth of body, dispropor- 

 tionate to their length 1 . In the earlier stages, when about 

 4*5 mm. in length, this flattening and depth of the body are 

 diagnostic. Posteriorly an abrupt narrowing occurs, and the 

 slender embryonic tail is continued as a tapering straight 

 process bordered by the embryonic fin, which runs from the 

 head dorsally round to the vent. The rays are longest at 

 the base of the slender caudal process. Another feature of 

 moment is the ventral projection of the abdomen, for it extends 



1 From the Researches, p. 8HO. 



