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 seirator) 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 twentj'-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 sout 

 contractus h V6ta.t sphi-rique, ils sont trop petits pour faire line image perceptible sur 

 la ratine, ct sont de nul effet. Dcs que I'animal est sur fond noir, les chromoblastes 

 se dilatent ; ils ^tendent de tons cotc^s des ramifications qui couvrent une grande sur- 

 face ; ils deviennent perceptibles et modifiont I'image r^tinienne. 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, a mesure qu'ils ^tendent leurs 

 ramifications sous I'hypoderme, on voit ce dernier tissu, k 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 Pal^mon sa couleur propre [rouge 

 brunatrc] sur fond noir. Quand les chromoblastes dilates se r^tractent de nouveau, 

 ce bleu, qui s'ost produit dans I'hypoderme et qui I'impregne, persiste pendant six 

 i sept hcurcs et disparait progre.ssivemcnt." 



The prawn depicted on Plate H {Bcnfhesicymus tcmneri) was brought tip 

 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 I'Aiiat. ct dc la Pliysiol., VIH. 401, 1872. 



