THE FLAT-FISH FAMILY 247 



is no doubt that when the eggs are shed from the roe of the fish, 

 the membrane closely envelops the yolk, and the wide space 

 separating the two is produced when the eggs come into con- 

 tact with the sea-water. The eggs were not hatched during 

 the Irish expedition, but stages of the larva are known from the 

 work of Professor Mclntosh and Mr. Holt at St. Andrews. 



In the embryo before hatching there is not much black 

 pigment : the coloured pigment is a pale yellow, distributed 

 somewhat uniformly over the head, body, and tail region, but 

 absent from the yolk sac and marginal fin-membrane. 



The newly hatched larva is described and figured by Professor 

 Mclntosh in the Seventh Report of the Scottish Fishery Board, 

 1889, but he gives no measurements. According to Holt's 

 observations the egg was nearly ready to hatch when about five 

 days old. The larva, half a day old, had a length of 3-99 mm., 

 or a little less than % inch. The mouth was formed, the pig- 

 ment extremely faint and without special arrangement. It was 

 absent from the fin-membrane, and there was no black pigment, 

 only the yellow. 



An older stage is figured by Holt. It was 4/65 mm. long, 

 less than i inch. The yolk was reduced to about half its bulk 

 at the time of hatching, and the lower jaw was more developed. 

 But the most striking change was in the pigment, the yellow 

 having darkened to a chrome tint, and black specks having 

 appeared. The pigment, moreover, now formed three distinct 

 bands across the tail, one behind the other, as in the lemon dab 

 and witch, but the bands did not extend on to the marginal 

 fin-membrane. 



Of the transformation stages we know nothing with certainty 

 at present, for among the minute specimens of flat fishes collected 

 at sea, this species has not been identified, at least not to the 

 present writer's satisfaction. But very small specimens in the 

 perfect or fully transformed condition were obtained in the 

 course of the Irish Survey. Several were captured in the shrimp 

 trawl in August 1890, at the depth of 80 fathoms, off the 

 Skelligs. These ranged in length from I T V to if inches. On 

 the following day more were taken at 52 to 62 fathoms in the 

 same neighbourhood ; these were from if to i4 inches. The 

 smallest of these specimens is represented in Fig. 113. It will be 

 seen that in this stage the transformation is very nearly complete, 



