254 STALK-EYED CRUSTACEA. 
whelmed to our eyes by the expansion of the red chromatoblasts under 
the influence of the darkness in which these animals live. According to 
Pouchet,* the pigments of the xanthic series (red, orange, and yellow) in 
Crustacea are contained in contractile anatomical elements, — the chromato- 
blasts, — while the blue pigment is never found in the substance of the 
chromatoblasts, but is held in free solution. Pouchet found that living 
prawns (Leander serrator) when placed in a vessel with a black bottom 
always assumed a brownish red color, but if they were transferred to a 
white-bottomed vessel they became yellowish, — the intrinsic color of their 
tissues. Extirpation of the eyes of the prawn had the same effect as a black 
bottom, specimens thus mutilated remaining permanently red. The change 
from yellow to red was accomplished much more quickly than the reverse 
change from red to yellow. In the latter case the change was effected in 
about twenty-four hours, during which the animal passed through a transi- 
tory bright blue stage, —a phase of color not exhibited during the passage 
from yellow to red. 
“Le microscope explique cette triple apparence. Quand les chromoblastes sont 
contractés 4 l’état sphérique, ils sont trop petits pour faire une image perceptible sur 
la rétine, et sont de nul effet. Dés que l’animal est sur fond noir, les chromoblastes 
se dilatent ; ils étendent de tous cdtés des ramifications qui couvrent une grande sur- 
face; ils deviennent perceptibles et modifient l'image rétinienne. L’animal, sous 
cette influence, deviendrait d’un rouge ou d’un rose franc, si un autre pigment ne 
venait rabattre la vive teinte des chromoblastes. Mais, 4 mesure qu’ils étendent leurs 
ramifications sous l’hypoderme, on voit ce dernier tissu, 4 leur voisinage, prendre une 
belle nuance cobalt plus ou moins haute de ton. C’est ce bleu qui sert de bruniture 
au carmin des chromoblastes et donnent au Palémon sa couleur propre [rouge 
brunatre] sur fond noir. Quand les chromoblastes dilatés se rétractent de nouveau, 
ce bleu, qui s’est produit dans Vhypoderme et qui l’imprégne, persiste pendant six 
& sept heures et disparait progressivement.” 
The prawn depicted on Plate H (Benthesicymus tanner’) was brought up 
from a depth of 860 fathoms and drawn as soon as it was taken from the 
trawl. The general color is a deep blood-red or crimson, passing into 
scarlet on the abdomen. The dorsal side of the first abdominal segment 
is adorned with a large squarish spot of a deeper red than the rest of the 
abdomen. This spot is repeated on the second, third, and fourth abdom- 
inal segments. On the third and fourth segments the spot is bright cobalt 
* Journ. de Anat. et de la Physiol., VIII. 401, 1872. 
