[ 228 ] 



On Some Colour Variations and Adaptations in Actiniae- 



By 

 Chas. L. Walton. 



The significance of the colouration of various Aetiniaria has been of 

 much interest to me for some time, and particularly the extreme 

 variability displayed by certain of the most abundant species. 

 Descriptions of colouration and coloured plates help but little toward 

 elucidating these problems, the examination of numbers of the animals 

 living in their natural environment being absolutely essential before 

 any conclusions can be drawn. 



Taken as a whole, the colouration of Actinians seems to come under 

 the following heads : — 

 I. Warning. 

 II. Aggressive. 



III. Protective. 



IV. Colours with some special physiological significance. 



Examination has shown that these leading features are not neces- 

 sarily confined to a species, or even to an individual, which may combine 

 them in varying degrees, though one is usually partially or wholly 

 dominant, this being chietly governed by the environment. In other 

 words, I believe that the colouration of a species or individual may be 

 adaptable to more than one end ; that local circumstances and environ- 

 ment govern this, and that those species which become most effectually 

 adapted to these environmental circumstances will be everywhere found 

 to be the most abundant. 



Naturally this adaptation is not confined to colouration, but is 

 observable in many other details, some of which will be mentioned, 

 but the colouration is the main factor to which I wish to draw 

 attention. 



I have assembled a considerable mass of data, from which I shall 

 here detail a selection of what I deem the most suggestive and 

 instructive. 



Actinia egiiina, Linn. This is quite the most abundant British 

 species, and is extremely variable in colour; shades of red, brown, 

 green, etc., alone or variously combined, are all abundant ; several of 



