74 
that the closest scrutiny was needed to detect the presence of 
the crab.” 
But the crabs also afford wonderful instances of protective re- 
semblance. Already during my Expedition to Siam in 1899— 1900 
I noticed many instances, and on my recent Expedition I have 
again observed numerous cases. Over and over again, when ex- 
amining the material from the dredge, especially from a bottom with 
fragments of coral and shells, it happened that, after I thought I 
had picked out every animal, some pebble began to move and 
was found to be a crab. To such a degree they resembled the 
pebbles, coral or shell fragments, that it was only when they 
started to move, they could be discerned as animals. To describe 
all "the cases would be too great a task, and, as the principle is 
the same, rather superfluous. It is especially among the Leucos- 
iids that such resemblance is found; also several species: of Par- 
thenope (Lambrus) are wonderfully protected, some by the long 
claws resembling an old piece of coral branch, while the body 
looks like an ordinary pebble, others by the carapace being ex- 
panded into flat crests which cover the legs completely so that the 
animal seen from above looks like an old bivalve shell, Fig. 10 
shows a fine instance of such protective resemblance. Alcock 
(Op. cit. p. 92, 104), records similar observations, accompanied by 
some fine illustrations. 
Another crab, which appears to me te present a very peculiar 
sort of protective resemblance, is Zebrida adamsii White (Fig. 11). 
This remarkable little crab lives on the sea-urchins, Sa/macis bi- 
color and Toxopneustes pileolus, and perhaps others; it devours 
the spines, tubefeet and pedicellariæ of the sea-urchin, generally 
following -one-area from the top downwards. The corispicuous co- 
loration, brown and white longitudinal stripes, together with the 
many curious projections on body and legs, produces a remark- 
able resemblance to the close set, short spines of these sea-ur- 
chins, especially of Toxopneustes pileolus, whose spines are like- 
wise white and brown. — This instance of protective resemblance 
can, of course, only have the meaning to protect the crab from 
… being devoured by fishes; for' the relation between the crab and 
the sea-urchin it cannot mean anything. But one cannot help ad- 
miring the smartness, so to say, of this crab to seek protection 
against its enemies by mimicking its own helpless prev. 
