380 
resemblance would be of any use — for, of course, it would not 
help f. i. an Asterias to be ever so much like another animal 
against being devoured by a Solaster. 
The bright coloration of Asthenosoma is regarded by Semon'!)y 
as a case of warning coloration, to teach its enemies to keep away 
from its poison spines. This may not seem unreasonable. 
An apparent case of protective resemblance is recorded by 
Doderlein?”), viz. Eucidaris metularia (Lam.), which was found 
to resemble to a striking degree the Millepores, on which it was 
found living, so that it looked like part of the Milleporan colony. 
That this is no real case of protective resemblance is evident from 
the fact that this Cidarid is by no means always found living on 
Milleporas; in fact, I have never seen it on a Millepora, although 
I have collected a good many specimens of this species. 
Some good cases of adventitious protection are known among 
Echinoids. It is well known that some Echimoids, especially of the 
genus Tripneusles, cover themselves up with pieces of algæ, shells, 
pebbles or small stones, some times to such a degree that it is 
hardly possible to distinguish them in their natural surroundings. 
This must certainly afford a good protection for them — though 
it is by no means effective against their worst enemy, man. (The 
Tripneustes-species are highly estimated as food). — A still better 
protection has been acquired by the small Gymnechinus pulchel- 
lus, which I found to cover itself with an empty bivalve shell, 
big enough to cover it completely, so that decidedly nothing but 
the shell could be seen from above.?) 
Several Holothurians living on sandy bottom in shallow water 
cover themselves with a fine coat of sand. A much better, and 
much more interesting kind of protection has, however, been adopted 
by Pseudostichopus trachus Sluiter, a Holothurian which is found in 
considerable numbers in places of about 100 fathoms depth in the 
Sagami Sea, Japan. It covers its whole surface with sponge spicules 
')) R.Semon. Im australischen Busch und an den Kiisten des Korallen- 
meeres. 1896. p 510. 
”) L.Dåderlein. Seeigel von Japan und den Liu-Kiu-Inseln. Arch. f. 
Naturgesch. 1885. 
DTR. Mortensen. Zoological Results of the Danish Expedition to Siam. 
ll. Echinoidea (I). Mem. Acad. R. d. Sc. Copenhague. 7 Ser. I. 1904. p.115. 
