228 
BULLETIN OF THE BUREAU OF FISHERIES. 
In such cases the problem of color is transferred from the animal to the plant, which 
relieves the present discussion of any particular consideration of the matter. It may 
sufiBce, therefore, to say that in such cases color is only of secondary or incidental bio- 
logical significance, and is meaningless in relation to any problem of adaptation or 
protection. In the words of Duerden, “The rich profusion and beauty of color in 
coral polyps certainly seems to have no protective or warning significance” (op. cit., 
p. i6). 
But even in organisms in which color is constitutional there is little or no relation 
to environmental influences. For example, many actinians an.d alcyonarians living 
under identical conditions have very different color features; and, on the other hand, 
species of widely differing habitats and diverse environments exhibit closely similar 
aspects of coloration. Furthermore, a species which shows remarkable color variations 
in a given habitat will often show the same variations through its entire range of dis- 
tribution. As an example of this may be cited the well-known case of the common 
Metridium marginatum. The world-wide distribution of this species (assuming with 
McMurrich its identity with M. dianthus), and the very similar aspects of coloration, 
illustrates the point under consideration, showing that conditions of environment or 
habitat have little to do with the character or variation of colors, at least so far as this 
species may have any significance. 
The influence of conditions of nutrition, as already shown by me in former papers 
(op. cit.), act in similar manner on Anthozoa. Actinians kept in the aquarium very 
soon show color changes indicative of lowered states of vitality, unless pains be taken 
to obtain approximately natural conditions. In the celebrated Naples aquarium this 
has been more successfully done than I have seen elsewhere. Here certain species of 
actinians have thrived for years with little loss of vitality or change of coloration. 
PHOSPHORESCENCE. 
Among the many various and complex phenomena of life few are more unique or 
obscure than that of phosphorescence, or vital luminosity, the former name being more 
or less a misnomer, since except in appearance there is little or nothing in common 
between the phenomena to which it was originally applied, and those associated with 
living things. However, the term has become so generally associated with all sorts of 
luminous phenomena of similar appearance, and devoid of appreciable heat, that its 
use is likely to continue; and if care be taken to discriminate no serious confusion is 
likely to arise. 
The occurrence of phosphorescence in many species, and in a wide range throughout 
the entire class, makes some reference to the subject more or less incumbent. While 
probably much more general in tropical and subtropical waters it is yet fairly common 
elsewhere, being well known throughout the region concerned in this report. 
Much speculation has been aroused concerning its use or significance, and various 
and conflicting theories projected. No attempt will be made here to review the subject 
historically, nor to cite the various differences of opinion which have grown up. 
