THE SINISTER GEPHALOPODS 



moray eel into a tank with a mud-flat octopus : one of 

 the eel's favourite dishes. The moray eel's sight is poor. 

 It started searching for the octopus, but the latter quickly 

 discharged its ink. Long after the ink had dispersed 

 (although traces of it remained, much diluted, in the 

 water) the eel persistently searched for its enemy, but 

 the ink in the water was evidently having a most remark- 

 able effect on the searcher. The eel would go right up to 

 the octopus again and again, touching it with its nose, 

 yet showing no excitement and obviously unaware that 

 it was in contact with its prey. It may be that one of the 

 purposes of the ink is to paralyse the olfactory sense of the 

 cephalopod's enemies, and that they are unable to attack 

 it without olfactory stimulation. Certainly large numbers 

 of octopuses and their kind are saved from destruction by 

 eels — which are their main predators — by discharging 

 their inky fluids. Yet in strong concentration the ink is 

 fatal to its owner : a fact proved by naturalists who have 

 caught small octopuses and put them into buckets ; after 

 which they have annoyed them so that they have dis- 

 charged their ink into the sea water in the buckets. 

 Every time the experiment has been made the octopuses, 

 surrounded by their ink in strong concentration, have 

 died in a few minutes. 



Oceanic squids vary from small, luminous deep-sea 

 species to huge creatures many feet in length. The giant 

 squid [Architeuthis) may grow to a length of fifty-seven 

 feet, with tentacles extended. Squids have eight arms 

 (like octopuses) but also two tentacles. The terms 

 "arms" and ''tentacles" are often confused. The Octo- 

 poda have eight arms only. The Decapoda (which in- 

 clude squids and cuttle-fish) have eight arms plus two 

 tentacles. 



The brain of the common octopus is well developed 

 (for the animal possesses far more intelligence than is 

 usually supposed). Certain nerves control the flow of 

 water into and out of a cavity in the mantle. 



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