466 MARINE INVERTEBRATES 



fish, however, is an animal not true to nature, but a composite, 

 having the attributes of the polyp and of the octopus, and the 

 name of a large ray of Southern waters, a real fish, the Cephalop- 

 tera, known in its localities as devil-fish. This monstrosity of the 

 novelist's imagination has, however, done more to acquaint the 

 general public with these interesting cephalopods than have the 

 descriptions of scientists. 



The giant squid, which is such a dangerous foe, has its own 

 enemy in the . sperm-whale. The cachalot swims through the 

 water with its lower jaw hanging, the cephalopod grasps the jaw, 

 and the whale then shuts his capacious mouth upon it. Whale- 

 men describe conflicts between these enormous creatures, the 

 whale always being the conqueror. Sperm-whales killed by man 

 often eject great quantities of the squids in their death throes, 

 showing this food to be almost their exclusive diet. 



The name " cephalopod," meaning "feet around the head," is 

 descriptive in part of their anatomy. The head is usually 

 marked off by a neck-constriction, and it bears two highly 

 organized eyes. The foot is fused in part with the head above 

 the eyes and around the mouth ; on the upper side it is divided 

 into eight or ten long arm-like processes, bearing suckers, which 

 act as organs of prehension. The under part of the foot forms a 

 tube called the funnel. Through the funnel the animal expels 

 water from the mantle cavity, and thus propels itself through 

 the water. 



The mantle covers the body of the animal, and is a cup-shaped 

 or conical envelope, open only at the anterior end, through which 

 project the head and siphon or funnel. It is attached to the 

 body by a line on the dorsal side, the anterior margin being free 

 and open, but provided with an arrangement of cartilages by 

 which it can be hooked on to the siphon, thus completely closing 

 the entrance to the mantle cavity. The mantle is very muscular, 

 and is constantly expanding and contracting, taking water into 

 the mantle cavity through the mantle opening for respiratory 

 purposes, or expelling it through the siphon for propulsion ; in 

 the latter case the mantle opening is closed at the moment of 

 ejecting the water. When the siphon is in its normal position 



