ZOOLOGY. 561 
origin of the same, is not yet well understood. At certain hours 
during the day, when it is cloudy for instance, those spots in the 
operated animals which were in a paralyzed state were scarcely to 
be perceived, and again in an hour or so later, they stood out in a 
very marked contrast, in color, to the rest of the skin, without 
the foundation color having changed. 
The power of bringing the color into harmony with the sur- 
rounding medium among the crustacea, was remarkably shown in 
the Palemon serratus. Animals from three to four centimetres 
long are the best to experiment upon, placed in porcelain vessels - 
with black or white bottoms. The crabs that fishermen bring 
ashore have a rose or a dark lily color; if they are put into ves- 
sels with black or white bottoms in twenty-four hours, they will 
assume a color wholly unlike each other. Those in the white dish 
are yellowish, almost colorless, as if they had just shed their skin, 
and those in the dark colored dish are of a brown red color. When 
changed the pale one into the dark colored dish, and vice versa, they 
change color in a corresponding manner. The change of a pale 
one to a dark color, was more rapid than the reverse. Under favor- 
able conditions we can create a yellow, red and blue Palemon. If 
a foot is removed when any one of these colors is present, and put 
into a solution of sugar, the three colors appear successively be- 
fore the eye. The microscope reveals the sequel to this. If the 
Pigment cells are pressed together like balls, then they are too 
minute to mirror themselves upon the retina. As soon as the an- 
imal is placed upon a dark ground the coloring cells are distended 
and send out little branches on all sides; then they become per- 
ceptible to the eye. The animal becomes red rose colored, when 
nothing weakens the lively color of the pigment cells; as the 
branches of the latter distend under the hypodermis they receive a 
cobalt color and the carmine of the pigment cells becomes thereby 
browned, and thus the Palæmon takes on a color corresponding to 
the foundation. If the coloring cells contract again, the blue re- 
Mains six or seven hours in the hypodermis and then gradually dis- 
appears. With the Palemon as with fish, the change of color is 
Xe result of visual impressions. — 
_ Among animals whose eyes Pouchet extirpated, a continuous 
dark color was observed and continued during the entire time, 
thirty -four days. By severing the nerves, an explanation of the 
nomena was not attained. 
AMER NATURALIST, VOL. VIII. 36 
