252 STALK-EYED CRUSTACEA. 



Squilla tenuirostris, from 90 to 100 fathoms, which is a great depth for 

 this shallow-water genus, is deep pink. The more strictly littoral Stomato- 

 pods, on the other hand, although more or less fos.sorial in their habits, often 

 displa}' conspicuous color patterns in various shades of blue, green, and 

 brown. 



The deep-sea free-swimming Crustacea consist of the Hoplopb.orida3, cer- 

 tain o-enera of Peneidte, a few species of Pasiphaeiidae and Sergestidoe, and 

 the deep-sea Schizopods. Of these, the Hoplophoridte are without exception 

 blood-red, bright crimson, or crimson lake. The Peneids are mostly red, in 

 a few cases fading to orange or milk-white. Halijwriis wqualis (405 fathoms) 

 is pink, Haliporus neptunus (1644 fathoms), Aristivus coritscans (561 fathoms), 

 Hemipeneus caipenfcri (1091-1310 fathoms), and Hepomadus tener (1310 

 fathoms) are orange colored. Bentkesicymus tanneri, a Peneid of a deep 

 red ground color, is remarkable for having a large patch of bright blue on 

 the back of the second, third, and fourth abdominal segments.* The deep- 

 .sea Pasiphaeiidaj and Sergestida9 are lurid red or else deep crimson or lake. 

 Among the Schizopods the various species of GnatJwphausia are bright red 

 or crimson. So are Eucopia and (according to Willemoes-Suhm) the eyeless 

 PetalophtJiahmis. Ceratomysis sjnnosa, a blind Schizopod from 782 fathoms, 

 is milk-white. 



'I'he differences in the coloration of littoral Crustacea that are exposed to 

 different degrees of light are sometimes very striking, individuals of the same 

 species often displaying various tints, accoi'ding as they live in the open and 

 near the surface, exposed to the full influence of the sun, or in deeper water, 

 en.sconced under stones or within crevices, and thus removed from the glare 

 of day. The pallor of most fossorial species is very marked, recalling the 

 ghastly appearance of cave inhabitants. 



In connection with the prevalence of red colors among the Crustacea 

 from great depths, certain experiments upon shore species are very sugges- 

 tive. S. Jourdain t has shown that Nika cdulis, which is brown in a bright 

 light, turns to red when kept in the dark. Ilippnlyte varians will change 

 from a lively emerald green to brown, if placed in partial darkness, while in 

 total darkness it assumes a red hue.J Such experiments as these go far 

 toward explaining the prevalence of red color among the Crustacea of the 

 deep sea. It is due to a modification of the pigments, induced by the dark- 



• Sec page 254. 



t Comptes Rciitlus, LXXXVIl. 302, 1S78. 



t See A. E. Malard, in Bull Sue. Piiilomath. dc Paris, S'""" Ser., IV. 28, 1892. 



