392 THE FLOUNDER FAMILY. 



yellowish white, of the early stage, to the ochreous tint of the 

 present one is a feature of interest. The latter begins in very 

 minute points over the head and body, gradually spreads and 

 supersedes the yellowish white, which disappears. The dif- 

 ferentiation of the two is clearly seen at certain stages, the 

 yellow being characteristic of the body, and the pale buff or 

 dull whitish of the marginal fin. Moreover, the disappearance 

 of the yellowish-white pigment from the edge of the marginal 

 fin, so conspicuous in the early larva, and which renders it so 

 easily observed in a glass vessel, is another alteration of moment. 

 The speckled condition may be associated with the more 

 helpless stage, when, perhaps, it frequently rests on the bottom, 

 but this is conjectural. At any rate, the border of the marginal 

 fin, at this and the post- larval stages, is so translucent as to be 

 generally invisible, only the pigment-touches arising from the 

 border of the muscle-plates being seen. The other parts of the 

 head and body, as well as the under-surface of the abdomen, are 

 speckled with ochreous and black pigments. The breast-fins 

 have their fan-like blades directed forward, so that the larva 

 seems to row itself onward by their rapid motion; the basal 

 part of each is also invaded by the yellowish pigment. The 

 great depth of the head and the prominent ridge over the 

 optic lobes of the brain are characteristic. The eyes are silvery 

 with black pupils, and as usual a dark arch occurs superiorly. 

 The skin- fold along the median line of the abdomen next 

 day was marked by a central gap, so that it formed two 

 portions, and the anterior one a day or two later became broad 

 and almost vesicular. Such changes, however, may have been 

 partly due to confinement. 



The next stage in the development of the sole was captured 

 in the bottom-net by Cunningham 1 at Plymouth in May, 

 1890, and in this the early post-larval stage is reached. The 

 notochord is bent up posteriorly, and the caudal fin-rays are 

 beginning to appear. The eye is bluish, and the auditory 

 vesicles are large. Definite pigment-spots occur on the dorsal 

 and ventral fin-membrane about six on the former and four 

 on the latter, as indicated in Cunningham's figure, which 

 1 Jour. Marine Biol. Assoc. May, 1891, p. 70. 



