544 r. W. (JAM15LE. 



Young specimens oE ballau wrasse were unfortunately not 

 available at Plymoutli, but this species would be an even 

 more suitable one for such an investigation. 



(2) Pigments and Colour Changes. 



In the case of Crenilabrus me lops the coloration is of 

 a barred type. Tlie head is marked Avith streaks of colour 

 associated with the brain and with the lateral line organs on 

 the operculum and jaws. The tail is usually marked by a 

 central black spot, and the greenish or yellowish trunk is 

 traversed by six or more vertical dark brown bars which 

 extend from the dorsal fin to the anal, but do not cover the 

 ccelomic region. This species in its young state is the most 

 abundant of the wrasses in Plymouth Sound. 



The arrangement of the pigment is as follows : Four 

 colouring matters contribute to this result — blue, black, 

 yellow, and red. Contrary to the statement by Krukenberg 

 that the blue colouring of wrasses is due to a special 

 pigtnent but is an optical colour merely, I find that in 

 Crenilabrus melops a blue substance is associated with 

 the skeleton in such a way as to give the young animal a 

 transparent pale blue tone when the chromatophores are 

 contracted. The nature of this substance, which, so far as I 

 know, lias not been previously recorded, is probably not 

 pigmental, nor has it yet been determined. The green 

 skeleton of Belone and the "vivianite" associated with some 

 old red sandstone fishes possibly contain allied substances. 

 Around the blood-vessels there is also a diffused, blue sub- 

 stance, which is most easily noticeable in the tins and the peri- 

 toneum, and forms a blue line along the aorta. The yellow and 

 red pigments form a network derived from yellow or orange 

 chromatophores scattered over the back and flanks and along 

 the fin-rays. The combination of this yellow network with 

 the underlying diffused blue pigment and the blue skeleton 

 gives a green tinge to the young fish, whilst the expansion of 

 red pigment gives a ruddy colouring; when both red and 



