398 THE FLOUNDER FAMILY. 



yolk appears like fine meshes over the surface. By trans- 

 mitted light the pigment is dark and finely dendritic. 

 Holt gives 2'02 mm. as the total length of his examples, 

 while those of one or two days were 214 mm., the yolk 

 reduced, and the oil-globules fewer; indeed, at St Andrews, 

 these appear to be in some cases fewer from the first. On 

 the fourth day he found the length 2'38 mm., the increase 

 being in the region behind the vent. The mouth is now 

 marked by a deep pit. In a few days the oil-globules dis- 

 appear, and patches of yellow pigment occur in some along the 

 dorsal and ventral fins. The usual changes in the development 

 and relations of the organs are carefully recorded by Holt. 

 Chief amongst these are the deposition of black pigment in 

 the eyes, and the great elongation of the region behind the 

 vent. The post-larval condition (Plate XIX, fig. 13) is 

 reached in eight or nine days, and then the yellowish pigment 

 acquires a greenish hue, while the dorsal fin is expanded in 

 the anterior region. The total length is now from 2'98 to 

 3' 10 mm. They are restless and hardy, as in the case of the 

 common sole. Holt also found them extremely hardy, so that 

 with very little attention they were easily reared in small vessels 

 to the post-larval condition. 



The next stage is given by Ehrenbaum, and measures 

 6'3 mm. The body of the fish is considerably augmented in 

 depth (Plate XIX, fig. 14), especially in the abdominal region, 

 while the anterior end has become more truncated. Pigment 



O 



has increased along the edges of the muscle-plates, and on the 

 ventral surface of the abdomen. The breast-fins are also much 

 larger. Only one or two indistinct touches of pigment of a 

 greenish-yellow colour occur, and thus the contrast with the 

 sole is pronounced. At the length of 7 to 8 mm. metamorphosis 

 takes place, fin-rays and interspinous processes are present, 

 and the left eye has appeared on the ridge. A notch superiorly 

 in the caudal region indicates a trace of the larval tail. The 

 pigment is still confined to the margins of the muscle-plates, 

 the head and abdomen. At 8'2 mm. in August both eyes are 

 on the right, and only a slight notch in front of the dorsal fin 

 indicates the passage of the left eye. Pigment is now grouped 



