ALLIES OF THE ACEPHALA 217 



must be of considerable value to them in escaping the 

 notice of enemies, as well as useful in coming unseen into a 

 school of small fish. 



Another and still more effective means of escaping from 

 the attack of a superior enemy is employed by the squid 

 when driven to its last resource. It has in its body cavity a 

 sac which secretes a black, inky fluid. A tube from the ink 

 sac passes to the siphon, and in the moment of need the sac 

 and the muscular mantle contract and force the black, con- 

 fusing fluid into the water. The squid then has a chance to 

 escape. 



Along the coast of Newfoundland giant squids, belonging 

 to a genus different from the one here described, are occa- 

 sionally brought up from the deep sea and stranded on 

 the shore. These monsters have a body about twenty feet 

 long, and some of their arms measure more than thirty-five 

 feet. 



The Octopus. A close relative of the squid is the much- 

 maligned octopus, or devilfish (Fig. 116, B). The body of 

 the devilfish is sac-like and has but eight arms. Although the 

 arms of these creatures may get to be several feet long, they 

 are not nearly so dangerous to man as their appearance 

 and stories about them might lead one to suppose. 



The Chambered Nautilus. Almost the sole representative 

 of a once numerous race living in the depths of the sea, is 

 the chambered, or pearly, nautilus (Nau'tilus pompil'ius, 

 Fig. 117). This species now has a restricted distribution in 

 the vicinity of certain south Pacific islands, such as New 

 Guinea and the Philippines. The nautilus lives on the 

 bottom, usually in water from one hundred to seven hun- 

 dred meters deep (three hundred and twenty-five to 

 twenty-three hundred feet). 



The shell of the nautilus is divided into compartments by 

 cross partitions. Each of these compartments represents a 



