546 V. vv. (JAMHLi';. 



nervo impulses act on the cliromatophores. The phenomena, 

 in fact, recall the pilo-tnotor or goose-skin reflex in man. 

 Recent physiological researches (Van KynVjerk) have shown 

 in certain Pleuronectids that the ganglia of the sympathetic 

 system supply each a definite transverse band-like region on 

 the upper side, and that these regions overlap one another 

 to the half of their width. Stimulation of these regions by 

 induction currents pi-oduces contraction of the cliromato- 

 phores. Section of the spinal nerves and of the rami com- 

 municantes of the sympathetic, leave the i-egions in question 

 dark and their chromatophores permanently expanded. 



This power of localised colour change is still very imper- 

 fectly understood. The development of the affected regions 

 has not been undertaken, nor is the heightened coloration 

 of the breeding season as yet in any way explained. It is 

 therefore of some interest to note that in the case of the 

 uniformly coloured adult Ctenolabrus rupestris I have 

 been able to observe the banded pattern appearing in the 

 post-larval stuge 10 mm. long. The pattern at that stage 

 differs but slightly from the livery of ''melops," Ijut the 

 difference is that in the former the pigmentation arises in the 

 form of these transverse bars separated by clear areas, whereas 

 in melops, so far as I have observed the species, the barred 

 pattern is inter-connected by diffused chromatophores. The 

 subsequent monochrome pattern of "rupestris " is evidently 

 dei"ived from this earlier-barred one by development of 

 interstitial pigment : but the presence of the bars even in the 

 adult is revealed at the moment when under stimulation the 

 skin becomes traversed by dark segmental bars alternating 

 with areas of pallor. 



(3) The Influence of Daj'light reflected from the 



Algal Backgrounds. 



Experiments on this problem were carried out as follows : 

 The young wrasses, obtained by hand-netting over Laminaria 

 fringes, were placed in clear glass vessels, and these, in turn. 



