'
THE SEA_S
in Crustaceans, in the squid and cuttlesh family, and in
sh.
Aniongst.the rst of these the most striking example,
which has
been
thoroughly investigated by Professors
Gamble and Keeble, is that of the little Æsop prawns
(Hippolyte).
little
never
more
than an
_
inch in length, are very commonon seaweed in rock pools
and on rockyboasts but are very difcult to discover
owing to the exactness with which they tone with the
background. '
'
.
.
'
Beginning with the birth of the prawn; when the young
batch
they are’colourless and almost transparent and
drift about in
sea for some time, being nally carried
inshore where, for the sake of the food and securit?
_
aorded’ them, they cling to the rst piece of seaweed they
’
meet.
They now beginto develop colour, a process Which
takes
place quickly and always results in the animal
_
assuming the exact shade of colour of the weed Which it
has chosen for its home.
If this is 3. red weed from deeper
water, the prawn becomes red, if a brown weed from the
-intertidal zone, it becomes brown, or if a green weed in
the rock pools near high—water mark, it becomes green
(Plate 66).
The process begins gradually but at the end
of a
week the match in colour is usually perfect and the
prawn almost impossible to detect.
_
If the Æsop prawn is driven fr0m its home by unfavour—
able
such as strong tides or currents, it searches
for a new home of the same colour, but should this be
impossible (as it may easily be-made in the laboratory
by placing collected prawnson weeds of different colour
-
from themselves) then the prawn changes itscolour to that
‘
-
-
'
the new home and at the end of a week will have
developed a new‘colour scheme just ‘as exact an imitation
its surroundings as Was the rst.
Quite independent
of these enforced changes of colour due to Change of sur-