482 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
matic plasticity of the animal. It is probable that in the fixed con- 
ditions of a colored environment the plasticity of the chromatophores, 
diminishing by degrees, would become nonexistent (after a long 
time). The color would then be constant. 
Would the chromotropism lose its synchromatic resonance also? 
I know nothing about this. But it is probable on a priori grounds 
that there are creatures which, having completely lost their power 
of changing color, because of the anatomical structure of their in- 
teguments, have preserved or evolved their chromotropic plasticity 
and their chromo-kinetic resonance of their instinctive movements. 
Such is the case of our Maja. 
And so we are brought back after all to the immediate subject of 
the present analysis. 
IX. THE “CHOICE” OF COLORS, AS INSTINCTIVE, VARIABLE SYN- 
CHROMATISM, DUE TO THE CHROMO-KINETIC RESONANCE OF THE 
ANIMAL. 
We are so fortunate as to be aided in this difficult question by the 
objective proofs which J/aja presents by its covering and as Hippolyte 
presented by its organic color. 
The covering indicates each time the chromatic past of the crabs, 
the environment in which the crabs have lived. The “choice” of 
colors presents itself then in the following aspect: 
§ 1. THe “CHOICE” or COVERING. 
The animal, put into a colored environment—green for instance— 
in acquiring under its direct influence, by chromo-kinetic resonance, 
the corresponding chromotropism (synchromatic), becomes chloro- 
tropic, and consequently negative in relation to other colors. If it 
finds colored papers, it can take (that is to say, approach) neither the 
red nor the white, etc., these colors making, in the green aquarium, 
negative spots (repellant) for the chlorotropically adapted animals. 
It will disguise itself, then, in such green as it encounters while 
wandering over the green surfaces. It will do the same in an en- 
vironment of any color, except black. 
It will now be understood, what would otherwise be inexplicable, 
why the old coverings in the experiments of chapter III, paragraph 
1, had no influence upon the color of the new covering. 
It will also be understood why one should not use too large or 
too numerous bits of paper, the characteristic color of the aquarium 
diminishing relatively its decisive influence. The bits of paper 
should not be, however, too small, the negative tropic surfaces ef- 
fecting, then, either no action at all or an action too weak to prevent 
the animal from approaching it. 
