194 NOTES AND iMEMOKANDA. 



alternate more or less in position with their dorsal fellows, and are 

 connected one with another by an irregular network of dark lines. 

 The pale autero-ventral blotches are of more variable occurrence, and 

 the ground colour and the colour of the dark markings are in no way 

 constant. 



On the south side of the Aquarium is a large tank devoted to bream 

 and wrasse. It is lined at the back and sides with rock-work of red 

 granite, now become brownish by the accumulation of foreign matter. 

 A large projecting boulder forms a cavern at the back of the tank, 

 much fre([uented by the prominent members of the wrasse community. 

 The bottom is gravel of a light colour. 



The wrasse with which we are dealing was pitched into this tank as 

 soon as its colours had been noted. It immediately bolted into the 

 cavern already mentioned, and, in the course of the initiation cere- 

 monies inevitable on the admission of a new member, was summarily 

 ejected a few minutes later. But, whereas it went in grey with dark 

 bars, &c., it came out green with only very faint grey marblings. The 

 sun being still in the east and the atmosphere dull, the illumination of 

 the tank was decidedly dim, but as the fish rested on the botton near 

 the glass its colours could easily be seen. After retaining the colour 

 phase just noted for perhaps a few minutes, the dark bars were 

 suddenly resumed within an interval of a few seconds, but the green 

 ground colour remained. The fish has since remained in this tank, but 

 varies constantly in colour, retaining, however, the general scheme of 

 grey markings on a green or olive-green ground. On the 2nd January, 

 1898, it was observed to be for a short time almost uniformly green, but 

 on the posterior part of the side, from the level of the soft dorsal back- 

 wards, it was noted that a number of the scales exhibited a pale 

 roundish spot. Such a marking could not have escaped notice at an 

 earlier date. It is, in fact, an approach to what we may call the typical 

 colouration of the species, in which every scale shows a pale spot and 

 the fins are similarly spotted, though the darker ground colour is 

 extremely variable. 



Our observation, such as it is, demonstrates clearly enough that the 

 uniform green, and the barred and patched liveries, can be achieved 

 by the manipulation of the chromatophores of a single individual, 

 according to the stimulus. It suggests, as we suppose, that the typical 

 spotted livery may not be distinct from the others, but does not go far 

 enough to show whether it is a question of the manipulation of chroma- 

 tophores capable of presenting the other liveries, or a gradual alteration 

 of the chromatophores themselves. As to the nature of the stimuli 

 which effect the colour-changes we have no evidence, except that the 

 colour environment is certainly not constant in its effect. For in the 



