3 6o THE WEBBED SEPIA. 



afford the slightest possible resistance to the water through which it passes, keeps its 

 velated arms stretched tightly over the shell, and then, by violently ejecting water from 

 the siphon, drives itself, by the reaction, in the opposite direction. 



The uppermost figure in the illustration shows the Argonaut in the act of swimming. 

 The extremity of the siphon is seen projecting immediately below the eye, and the 

 reader will at once understand that if the action forcibly ejects water from the tube, 

 the effect will be to drive the animal rapidly in the contrary direction, /'. e. from right 

 to left, as seen in the engraving. The third figure represents an empty shell, and is 

 given for the purpose of showing the partially spiral and deeply grooved keel, as well 

 as the extreme tenuity of the she 1 itself. 



The animal, or poulp, is very slightly connected with the shell, and, when captured 

 in a net, will sometimes voluntarily leave its home. Many persons have therefore 

 thought that the poulp was not the fabricator of the shell, but only an intruder on the 

 premises of the rightful owner, having taken possession of the shell as a defence for its 

 soft body, just as the well-known soldier or hermit crab arms its soft and unprotected 

 tail with the shell of a whelk, periwinkle, or a trochus. This opinion, ingenious and 

 deserving of examination as it was, has, however, been proved erroneous by a number 

 of experiments, which have shown that the Argonaut is not only the occupier, but the 

 architect of its graceful dwelling, and that the expanded arms are at once the furnish- 

 ers of the material and the executors of the work. 



The precise food of the Argonaut is not ascertained, but Mr. Bennett presumes that, 

 as he always found the globular and translucent, but empty shells of the hyalea, one of 

 the wing-footed marine species, adhering in numbers to the disks on the Argonaut's arms, 

 these creatures must have been captured and devoured by the more powerful mollusc. 



As the various cephalopods are so numerous as to preclude all possibility of figuring 

 and describing each species, we must therefore content ourselves with a typical form 

 of each family, and a general account of its members. 



The species belonging to the family of the Octopodidae, or Eight-armed Cuttles, pos- 

 sess no external shell like that of the nautilus, its place being taken by two short styles 

 or " pens " in the substance of the mantle. There are eight arms, unequal in length, 

 and furnished with double or single rows of the suckers which have already been 

 described. 



They are solitary beings, voracious to a degree, and so active that they find little 

 difficulty in capturing their prey, or in escaping from the attacks of their enemies. 

 Even when pursued into the narrow precincts of a rock pool, the creature is not easily 

 caught. When threatened, or if apprehensive of danger, the Polypus, as the animal 

 was formerly called, darts with arrowy swiftness from one side of the pool to the other, 

 and at the same time so discolors the water with the contents of its ink-bag, that its 

 course is not perceptible, nor, until the water dias become clear again, can the precise 

 locality of the creature be discovered. Even if detected, it is not easily captured, as it 

 has a knack of forcing its unprotected body into some crevice, so that no hold can be 

 taken of it, and then affixing itself by its suckers to the rock with such wonderful 

 tenacity that it can hardly be detached as long as life remains. 



One example of this family is the WEBBED SEPIA, a very curious animal, found on the 

 coast of Greenland. Its color is violet, and the arms are united by a web almost to 

 their tips. The suckers are set in single rows. Only one species of this genus is 

 known. 



In the Octopods the suckers are set directly upon the arms, and the eyes are fixed in 

 their orbits ; but in the Decapods, another section of these creatures, the suckers are 

 placed on footstalks, and armed with a bony ring on each. The eyes are movable, and 

 the shell is internal, lying loosely in the mantle. This so-called shell has, however, no 

 real title to the name, being either a spear-shaped body of a horny substance, such as 

 is popularly known by the name of sea-pen, or a curious aggregation of chalky particles, 

 familiar under the title of "cuttle-bone." This "bone " is not attached to the animal 

 by any muscles, but lies loosely in a kind of sac in the mantle, and will drop out if the 

 sac be opened. 



