81 
standing out as a close coat of fine very loose sitting bristles (Fig. 16). 
This must give a very perfect protection; everybody who has tried 
to handle it with the fingers can realize the result, when a fish 
would try to swallow this séa-cucumber; it would get the mouth 
full of the spicules and most probably leave the animal alone after 
having tried it once. I am not aware that any experiments have 
been made with feeding fishes on this Holothurian, but the result 
can hardly be doubtful. — A similar adventitious protection is found 
in Pseudostichopus occultatus v. Marenzeller and also in Meseres, 
especially M. hyalegerus Sluiter. 
It is quite possible that the very conspicuous black coloration 
in some Holothurians — the more conspicuous when they live on a 
white, sandy bottom — serves as 
a warning coloration. Those forms 
which have Cuvierian organs pos- 
SESsS a very effective means of pro- 
tection; those peculiar sticky, white 
threads, which dart through the wa- 
ter like arrows (always with the 
end bent, so that the foremost point 
Is about one centimeter behind the 
tip), entangling anything they meet, 
must be very dangerous weapons. fn dorsal and ventral vis. NL sie. 
I have seen crabs helplessly en- 
tangled in them. — On the other hand not all the Holothurians 
Possessing Cuvierian organs are conspicuously coloured. Some forms 
are grey, spotted, that is to say protectively coloured in the same 
Way as are so many other animals living on sandy bottom. 
Possibly another case, observed at the Philippines, should be 
interpreted as a warning coloration. On a coral reef in Taba Bay, 
Mindanao, I observed on some big sponges, which seemed to be 
of the well known form Poterion Neptuni, numbers of small, some 
10—.12 centimeters long, Synaptids crawling on the outer surface 
of the sponge, very conspicuously coloured, whitish with longitud- 
inal blackish stripes. Experiments alone could decide, whether this 
is really a warning coloration; protective coloration would seem 
Out of question here — there could in that case only be the pos- 
Sibility that they are mimicking some Nemerteans; but then it is 
6 
Vidensk. Medd. fra Dansk naturhist. Foren. Bd. 69. 
