CONCEALMENT AND COLORS IN CRUSTACEA—MINKIEWICZ. 483 
Again, it can be seen why the crabs, in numerous experiments, 
selected all the synchromatic papers, without having touched the dis- 
cordant papers, although these were present in considerable quantity. 
§ 2. THe CHOICE OF ENVIRONMENT. 
The animals disguise themselves in preparatory aquaria of a cer- 
tain color, containing only papers of the same color. Under the direct 
action of this environment they acquire the corresponding chromo- 
tropism. Once put into the conditions where chromotropism can 
be attained, as in our experiments of chapter III, paragraph 2, in 
the aquarium divided in differently colored halves, the crabs proceed 
toward the corresponding environment. The covering itself plays no 
part in this phenomenon. It is of use only to the experimenter, con- 
stituting a true recognition mark, thanks to which one cannot be 
deceived as to the chromatic past of the animal. 
In order to confirm this manner of regarding the facts, I went 
again to Villefranche, especially to perform some new experiments 
and to procure some irrefutable data. 
1°. IL raised several A/aja during a certain time in colored aquaria, 
without giving them material with which to cover themselves. I 
then studied their reactions with relation to the colored surfaces of 
another aquarium divided in two. The corresponding chromotrop- 
ism was established without covering. 
2°, In an aquarium of any color whatsoever, for example red, I 
have noticed the “ favorite” corner where my thigmotropic crabs 
habitually crowded together. Afterwards I have changed that cor- 
ner to a different color, for instance green. 
Then the crabs harmonizing with red no longer came into this green 
corner which now presents a surface negatively tropic. Many times 
I found them near the limit of that color, where they stopped and 
after a short time drew back. 
Then I changed the discordant corner. The crabs frequented it 
again, but now they could not go beyond the boundary of the new 
negative corner. ‘These two recent series of experiments are, it seems 
to me, sufliciently conclusive. 
§ 3. Errors or INSTINCT. 
“ Errors of instinct ” no longer exist in our explanation of the facts 
of self-concealment. 
In the black aquarium, the chromotropic action of the environment 
being nil, each colored surface (papers) which might be found would 
exercise a positive action; the animal would go toward it and would 
clothe itself eventually with colored paper and not with black paper, 
which exerts no action. It may take some occasionally, if it meets it 
by chance, on its way toward the tropic paper; but that only very 
rarely occurs. 
