CONCEALMENT AND COLORS IN CRUSTACEA—MIN KIEWICZ. 477 
If green did not exist, the scale of tropic values would be: 
(5) (—) black — red — blue — violet — white (+), 
normal, according to Loeb’s theory. 
But the green possesses the same influence over the Pagurids as over 
the human eye; consequently the tropic scale appears quite different: 
(6) (—) black > red — yellow — blue — violet > green — white (+). 
It is certain that it is not the intensity of color that plays a pre- 
ponderant role here; careful comparison of the tropic reactions of 
the Pagurids (positive animals) with those of Lineus (negative) 
and especially with those of Zozez (positive), in relation to the same 
chromatic rays, gives sufficient proof. In the case of the Pagurids, 
the yellow is much less tropic, not only with regard to green, but also 
in relation to colors as slightly intense as blue and violet. 
VIl. THE EXPERIMENTAL INVERSION OF CHROMOTROPISM. 
Thus, each chromatic ray has a specific action, autonomous and 
independent of the action of the other chromatic rays and of that of 
white light. 
But this statement, although very important, would not give us 
the means of examining carefully the instinct of self-concealment, 
had I not obtained at the same time the inversion of chromotropism. 
After long and fruitless research with isotonic solutions of various 
chlorides, with concentrated sea water, etc., I accomplished my ends 
in quite an unexpected fashion, by an extremely simple process, 
namely, the addition of distilled water (from 25 to 80 cubic centi- 
meters to 100 cubic centimeters of sea water). Placed in that solu- 
tion Lineus ruber becomes the next day wholly janthinotropic. While 
remaining negative in relation to white light, it turns toward the 
most refrangible rays of the spectrum as decidedly as it had previ- 
ously avoided it. It is by this process that I have been able to sepa- 
rate chromotropism from phototropism, and thus prove in an indis- 
putable manner its functional autonomy, which I have mentioned 
above. 
If, before this, the normal Zineus, put into a horizontal tube par- 
allel to the luminous source and placed behind a series of differently 
colored plates, all assembled under the red plate or, in its absence, 
under the one which allows the least refrangible rays to pass, they 
will now all assemble under the plates which allow the passage of the 
most refrangible rays. 
Thus, the change in the physiological state of the organism under 
the influence of the dilution of the surrounding medium brings about 
a change in all the reactions due to chromotropism. 
