202 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 fossorial in their habits, often 
display conspicuous color patterns in various shades of blue, green, and 
brown. 
The deep-sea free-swimming Crustacea consist of the Hoplophoridx, cer- 
tain genera of Peneide, a few species of Pasiphaeiide and Sergestide, and 
the deep-sea Schizopods. Of these, the Hoplophorid 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. Haliporus aqualis (405 fathoms) 
is pink, Haliporus neptunus (1644 fathoms), Avristeus coruscans (561 fathoms), 
Hemipeneus carpenteri (1091-1310 fathoms), and Hepomadus tener (1310 
fathoms) are orange colored. Lenthesicymus 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 Pasiphaeiidee and Sergestide are lurid red or else deep crimson or lake. 
Among the Schizopods the various species of Gnathophausia are bright red 
or crimson. So are Hucopia and (according to Willemoes-Suhm) the eyeless 
Petalophthalmus. Ceratomysis spinosa, a blind Schizopod from 782 fathoms, 
is milk-white. 
‘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, according as they live in the open and 
near the surface, exposed to the full influence of the sun, or in deeper water, 
ensconced 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. §. Jourdain ¢ has shown that Nika edulis, which is brown in a bright 
light, turns to red when kept in the dark.  /ippolyte varians will change 
from a lively emerald green to brown, if placed in partial darkness, while in 
total darkness it assumes a red hue.t 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- 
* See page 254. 
+ Comptes Rendus, LXXXVII. 302, 1878. 
¢ See A. E. Malard, in Bull. Soe, Philomath. de Paris, 8°™* Sér., IV. 28, 1892. 
