88 ANIMAL FORMS 
into the large mantle cavity within the body, a set of valves 
prevents its exit through the same channels, and upon a 
vigorous contraction of the body walls the water is forced 
out rapidly through the small opening of the funnel, which 
Se 
Fig. 52.—Cephalopods. Lower figure, the devil-fish or octopus (Octopus punctatus). 
The upper figure represents the squid (Loligo pealii) swimming backward by 
driving a stream of water through the small tube slightly beneath the eyes. From 
life, one-third natural size. 
drives the animal backward after the fashion of an explod- 
ing sky-rocket. In this way they usually escape the fishes 
and whales that prey upon them, but an additional device 
has been provided in the form of a sac within the body, 
whose inky contents may be liberated in such quantity as 
to cloud the water for a considerable distance, and thus 
enable them to slip away unseen into some place of safety. 
Most of the cephalopods are further protected by their 
ability to assume, like the chameleon, the color of the object 
