MEANS OF PROTECTION. 33 
when left exposed by the retiring tide, while the short flesh-coloured 
tentacles, which are the breathing organs, protrude through the sand. 
These readily come off, so that if the Eolis were to be seized by a 
fsh it has some chance of escaping while its assailant endeavours to 
eet rid of the small tentacles which only tickle its mouth, without 
a} peasing its hunger. Most probably the fish learn by experience not 
to attack these helpless looking objects. 
Those common shellfish, the Purpura lapillus, which are so well 
:nown to every visitor to the sea-side, are mostly protectively coloured, 
,e following numbers will shew, those that do not need protective 
colour being situated under very thick fucus are white, but this is more 
particularly due to being continuously rubbed by seaweed. 
Purpura in a thick bed of fucus. Out of 25 examples collected, 
23 were quite white. 
2 greenish yellow from thin growth of green algze. 
On rocks covered with green and small red sea-weeds, the numbers 
23 brown. 
6 dirty yellow. 
I grey. 
On rocks thinly covered with green weeds and small fucus there were 
43 overgrown with sea-weed. 
41 not overgrown. 
Of these the majority were, when the sea-weed had been pulled off, 
ofa dirty yellow colour. 
The colours of those on rocks partly overgrown with Fucus Ser- 
ratus and Vesiculosus, where there was no green alge were 
134 yellowish. 
25 white. 
2 dark yellowish brown. 
I orange. 
1 greenish, but not by alge, 
5 worn. 
The Limpets (Patella Vulgata) are protected by the sea-weed 
from the action of the waves; those which are surrounded by weeds 
being much fresher than the unprotected ones, though some of the 
larger ones get worn at the top. 
But it is from Entomology that most instances of Protective 
Resemblance can be taken. 
The Privet Hawk Caterpillar (Sphinx ligustri) harmonises well 
with the bright green leaves of the lilac ; the purple and white bands 
serving to make the resemblance more perfect by dividing the green* 
as tl 
were 
