76 IOWA STUDIES IN NATURAL HISTORY 
tacles of Physalia, or the Portuguese man-of-war, while the lat- 
ter takes toll by capturing an occasional fish. I have no doubt 
that the same relation exists between certain Meduse and little 
fishes which live in their gastric cavity. 
The coloration of most of the crabs is in general such as to 
render them inconspicuous in their natural habitat. It re- 
sembles the original type of camouflage of ships during the war 
just ended. It seems evident, however, that the crustaceans 
adopted the more advanced style of camouflage ages before this 
world war. Those who have seen the later development in ship 
painting have been much impressed by the bizarre patterns in 
sharply contrasting colors that make a vessel look like a crazy 
piece of patch-work. Black, white, blue, gray, even some yellow 
and red, strike one as better adapted to advertisement than to 
concealment. I myself have hardly been convinced that the 
vessels have thereby been rendered inconspicuous and have 
been slow to believe that this device is particularly effective. 
Captain Gladwin of the ‘‘Parima,’’ however, tells me that he 
has found it very difficult to see these ships at night and other 
times of poor visibility, although he is somewhat skeptical as to 
the effectiveness of their coloration in broad daylight. 
Now it is a fact that sharply contrasting color markings do 
destroy the apparent outline of a body that would otherwise 
have its contour betrayed, and this may account for the colora- 
tion of certain brightly marked crustaceans. Or these colors 
may merge together so as to be inconspicuous at a distance, 
although they are striking on close view. For instance, Por- 
cellana sayana, a very gaudy little crab taken from an old 
Strombus shell, was greatly flattened both in body and legs, and 
its general color was a bright pinkish brown or terra cotta; but 
the entire dorsal surface was ornamented with sharp round 
‘‘polka dots’’ of pure white, each spot being further accentu- 
ated by a sharply defined border of deep red, as if to bring the 
spots into the boldest possible relief. It is hard to explain such 
a pattern on the principle of protective coloration, but it seems 
to me possible that at a comparatively short distance these col- 
ors might merge so as to be quite inconspicuous on the sea-bot- 
tom. 
Great quantities and many species of crustacea were secured 
