METHODS OF ATTACK AND DEFENCE 93 



pools is of value in concealing the anemone from its prey 

 rather than from enemies. 



In spite of its chance nature, the menace to certain forms 

 from being settled upon by other animals is so serious as 

 to have led, as we have seen, to the elaboration in certain 

 cases of special cleansing organs. In other cases it would 

 appear as if this chance factor had been brought under 

 control, and, from being a menace, had been turned to the 

 positive advantage of the animal. 



Leaving the subject of encrustation, we now turn to a 

 consideration of the stratagems and weapons employed in 

 the direct conflict between hunter and hunted. 



Hiding. — It is a commonplace feature of the struggle 

 for existence among animals that the weak find safety in 

 hiding. As Fredericq (1889) puts it, " V animal chasse se 

 cache,'' and there are manifold ways in which the weaker 

 forms elude pursuit : by hiding under stones and seaweed, 

 by burrowing, by taking refuge in shells (hermit-crabs), and 

 so on. The habit of burrowing is very common on the shore 

 and indeed in marine forms generally. On the shore, it is 

 doubly valuable as securing immunity both from enemies 

 and wave-shock. All phases of the habit are exemplified : 

 from the swimming crab, which merely shovels sand over 

 its body by means of the last pair of paddle-like thoracic 

 limbs, through the numerous Annelids, such as the lug- 

 worm, to the highly specialised species such as the ship- 

 worm {Teredo), and the Piddock (Pholas), which excavate 

 wood and rock respectively. A discussion of commensalism, 

 which perhaps represents an elaboration of the hiding habit, 

 is reserved for a later chapter. Another obvious means 

 of securing safety is by rapid flight or by its antithesis 

 " death feigning." 



" Death-Feigning '* or Hypnosis. — Certain animals when 

 disturbed show a sudden complete cessation of activity 

 akin to death. A similar state can also be induced experi- 

 mentally in a number of forms. As Thomson puts it, " in 

 the state of animal hypnosis, seen for instance when a snake 

 * becomes a stick,' there is a sleep-like inability to move 



