CONCEALMENT AND COLORS IN CRUSTACEA—MINKIEWICZ. 479 
It has long been known that there exists a close relation between 
the phototropism of an animal and the intensity of the hght to which 
it is subjected. 
Groom and Loeb®@ first on the larve of Balanus and later G. H. 
Parker on the copepod Labidocera; S. J. Holmes on the amphipod 
Orchestia and on the flagellate Volvox; G. P. Adams on the annelid 
Allolobophora, ete., have shown that the changes from positive to 
negative phototropism, or the reverse, are produced under the influ- 
ence of the intensity of the light alone; that is, of the amplitude of 
the waves of the luminous radiations. 
It is not impossible, then, at least a priori, to find analogous cases 
in which the inversion of the chromotropism might be produced 
under the sole influence of the wave length of the luminous radia- 
tions, otherwise called their chromatic quality. 
Of course, this phenomenon can be established only with regard 
to animals which are extremely sensitive to luminous agents. 
They must be endowed with such plasticity of their sensorimotor 
organization that its state is capable of being changed under the 
direct action of the chromatic environment and that this change may 
be manifested by their tropic movements. 
The number of such creatures is evidently very small. 
At present I know, belonging to this category, only the little 
shrimps of the genus Hippolyte (H. varians) and the self-disguis- 
ing crabs. 
It is as a result of the work of two English biologists, Messrs. 
Keeble and Gamble,’ that I have recognized this phenomenon 
among the Hippolyte. I give here some passages from their first 
work: 
That the prawns exert powers of selection with respect to their weed will 
be readily realized from plates 32 and 33, figures 1 to 9, representing prawns 
placed in a dish with sea water, to which subsequently pieces of different 
coloured weeds were added. The prawns were left free to select their weeds, 
and ... they succeeded in making wonderfully accurate colour matches. . 
The brown variety of Hippolyte varians (mature specimens) abounds amongst 
the masses of brown Halidrys siliquosa which flourishes in the “ Laminarian 
zone.” ... Young specimens of a uniform brown tint occur chiefly among 
the fronds of Dictyota dichotoma. Mature green prawns are somewhat rare 
at Piel, though young ones are plentiful in the clear and shallow water of the 
Zostera pools. Red, again, is not a tint commonly found in full-grown Hippo- 
lyte varians at Piel, though a few large and many small pink specimens were 
from time to time discovered. Very probably the somewhat muddy water, 
stunted weeds, and the comparative scarcity of clean red weed are the causes of 
the rarity of this form. 
4Groom u. Loeb: Der Heliotropismus der Nauplien von Balanus perforatus 
und die periodischen Tiefenwanderungen pelagischer Tiere. Biol. Centralbl., 
bd. 10. 
+ Keeble and Gamble: Hippolyte varians, a Study in Colour-change. Quart. 
Jour. Micr. Se., t. 48, pp. 601-603. 
