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 
