MOLLUSKS 



105 



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 rapidlv through the small opening of the funnel, which 



FIG. 58.- -Cephalopoda. Lower figure, the devil-fish or octopus (Octopus punctatus). 

 The upper figure represents the equid (Loligo pealit) 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 



