THE FLOUNDER FAMILY. 325 



presented no embryonic rays in the caudal ; indeed, these did 

 not appear for some time. Mr Holt's specimens therefore were 

 probably more advanced at the period of hatching. No mouth 

 is visible, and the oesophagus ends blindly in front. With the 

 exception of those on the head, the yellow chromatophores are 

 still rounded, though, as a rule, the pigment is branched at or 

 shortly after hatching. In a lateral view, the yellow chromato- 

 phores are grouped chiefly at the dorsal and ventral margins of 

 the muscle-plates, and on the rectum ; the tip of the tail is 

 devoid of them. Besides the yellow, very finely ramose black 

 pigment-corpuscles occur on the head, and amongst the yellow 

 along the body, but they are not easily seen after the yellow 

 chromatophores become stellate, and in some specimens they 

 are late in appearing. The upper part of the head is chiefly 

 occupied by black pigment. A change must thus ensue before 

 the pigment is grouped into bars, for it is somewhat general at 

 this stage. The lumen of the gut has not entered the oblique 

 portion of the rectum, and the pre-anal region of the marginal 

 fin is small at this stage. A more advanced condition of the 

 pigment is shown in a specimen (also removed from the 

 capsule) on the 5th April. Both yellow and black chromato- 

 phores are finely branched. The variability in regard to the 

 development of the pigment is further shown in the sketch 

 of an example three days later, viz., 8th April, in which it is 

 now grouped in bars, — that is to say, at certain parts the 

 extension of the chromatophores is more pronounced than at 

 others. Thus the head and the region of the body-proper have 

 yellow and black pigment, the latter along the dorsal and 

 ventral edges of the muscle-plates, with a special area at the 

 rectum, and three bars behind it, that near the tip of the 

 tail being mostly black, though a few yellow chromatophores 

 are present. The eyes also have pigment-specks; the caudal 

 shows embryonic rays. The yolk has considerably diminished. 

 The otocysts are still elongated from before backward, but 

 present a double outline from the differentiation of the capsule. 

 The larvae with a large amount of yolk swim with a wriggling 

 movement. 



They daily increased in size and activity, and the five 



