THE FLAT-FISH FAMILY 22$ 



of May, according to Mcintosh and Prince, the larvae did not 

 escape from the egg until the twelfth day ; the difference 

 is due to difference of the temperature at which the eggs 

 were kept. 



The newly hatched larva was 2 •66 mm. long (a little more 

 than yV^h of an inch). Its chief distinction as compared with 

 the larva of the flounder is that the coloured pigment is lighter, 

 being of a lemon-yellow tint instead of chrome yellow. At first 

 there is no pigment on the fin-membrane. Professor Mcintosh 

 kept the larvae alive at St. Andrews for eleven or twelve days, 

 and gives a figure of one eleven days old. The yolk was then 

 all gone, the mouth and jaws were well developed, and there 

 was pigment on the fin membrane. The pigment was present 

 all along the tail, not forming a distinct band as in the flounder. 



The subsequent stages of this fish taken at sea are difficult 

 to distinguish with complete certainty from those of the plaice. 

 Numbers of little flat-fishes belonging to one or both of these 

 species in all stages of their transformation from g mm. to 32 

 mm. in length (less than i^rd inch to i^inch) were taken in the 

 month of May during the Irish Survey at depths from i to 32 

 fathoms. They were captured in tow-nets attached to the 

 trawl-beam. Mr. Holt has figured a series of stages considered 

 by him to belong to the dab. They are distinguished from the 

 similar stages of the plaice by the following differences : the fish 

 in the same stage of the rotation of the eyes is longer than the 

 plaice, the body is not so broad in proportion to its length, that 

 is the little fish is more slender in form, and the eye is some- 

 what larger in proportion to the head. Considering that when 

 first hatched the larva of the dab is little more than half the 

 length of that of the plaice, it is singular that it should be longer 

 than the plaice during the process of transformation. There are 

 no definite peculiarities by which in these stages the plaice and 

 dab can be distinguished. The red spots of the plaice are not 

 }-et distinctly developed, and the lateral line is not to be detected, 

 so that the curve in it which distinguishes the older dab is not 

 available. The young flounder can be recognised with certainty 

 by the number of the fin-rays,, but the plaice and dab in the 

 adult condition agree in this particular, so that it is of no use to 

 count the fin-ra}'s of the young specimens in order to discover 

 whether they belong to the one species or the other. 



Q 



