48 THE HAUNTS OF LIFE 
nate carapace of a rock-lobster, the unbreak- 
able shells of molluscs, the scales of fishes 
often sharp and formidable, and so on up to 
the complicated encasement of the edible 
turtle. 
MASKING 
The “walking wood of Birnam” was an 
episode in Scottish history, immortalised in 
Shakespeare’s Macbeth, where a band of sol- 
diers camouflaged themselves by cutting down 
branches of trees and carrying these with them 
as they stealthily advanced. So some crabs on 
the seashore fix seaweeds on the back of the 
shell and mask themselves effectively. They 
can steal upon their victims; they can efface 
themselves in the eyes of their enemies. Some- 
times the cloak consists of zoophytes, or pieces 
of sponge, or half of the tunic of a sea-squirt; 
but oftenest it is a cloak of seaweed. It is as 
if the crab carried a garden on its back. The 
camouflaging is often shown by the sand-crab 
(Hyas araneus) and by the narrow-beaked crab 
(Stenorhynchus longirostris) ; but it is seen in 
many others. The disguising seems very de- 
liberate on the crab’s part, and if the disguise 
is picked off, the crab often sets about clothing 
