434 -uit. e. w. l. holt — studies in [May 1, 



of the preserving fluid. The scales and sensory filaments of the 

 under surface are perfectly normal, subject to the trifling excep- 

 tion just noted, and have therefore been omitted from fig. B. It 

 may be remarked that in North-Sea Soles filaments extend on to 

 the bases of the first few dorsal fin rays, but otherwise have the 

 same distribution as is depicted in Cunningham's figure. 



The left eye is situated nearly opposite to the right eye, but is 

 slightly dorsal to it, and about half a length further back. Kelative 

 to the mouth the two eyes occupy nearly the same position, the 

 difference being accounted for by the greater length and dorsal 

 displacement of the gape on the left side. But, whereas on the 

 right side the whole of the iris is exposed, and the whole eye is 

 somewhat elevated and within certain limits freely movable (either 

 by the muscles or by the peculiar mechanism dealt with in the pre- 

 vious section of this paper), on the left side the eye is to a great 

 extent embedded in the skin (see fig. B). Only about half the iris is 

 visible, and even some part of the lens is obcluded, and the sensoiy 

 filaments, which extend right up to the cornea on the ventral side, 

 must, when erect, have considerably interfered with the animal's 

 vision. The whole eye is antero-ventrally rotated from what we 

 may suppose to have been its original nearly lateral aspect, and 

 I should think the fish could see but little except in the directions 

 indicated, while the prominence of the lips must have been a 

 further impediment to its sight. No movement could have been 

 possible except such as involved a general movement of the skin 

 in this region ; but, as the skin is always loose here to allow of the 

 expansion of the accessory visual sac, one may suppose that the 

 eye may have been shifted to whatever extent the length of the 

 eye-muscles permitted. The appearance it presents is that of 

 being gradually overgrown by the skin, or of being withdrawn by 

 some internal agency within the tissues of the head. 



The whole of the left surface of the fish is absolutely devoid of 

 pigment; with the exception of a slight extension of colour below 

 the mouth, which I have already attributed to post-mortem 

 changes, and of certain patches of colour on the caudal fin and a 

 small dark spot near the posterior end of the body. Such markings 

 of the extreme posterior region of the under surface are, however, 

 as often present as absent in normal Soles. 



The left eye is as bright as its fellow of the opposite side and 

 of the same colour, and, staring out of a deacl white surface, 

 presented rather a bizarre effect in the fresh condition. 



The whiteness of the underside is perhaps one of the chief 

 peculiarities of the specimen. The Cyclopean condition, compara- 

 tively common in the Flounder (Pl.jlesus) and, according to my 

 own experience, commonest of all in the Turbot (Rh. maximus), 

 is always accompanied by a more or less complete pigmentation of 

 the blind side. In fact, as has been pointed out by Cunningham 

 and MacMunn \ complete ambicoloration has been observed only 



1 " On the Coloration of the Skins of Fishes, especially of Pleuronectidae," 

 Phil. Trans. 1894, p. 806. 



