306 THE WEBBED SEPIA. 



As has already been mentioned, the respiration is achieved by the passage of water over 

 the double gills or branchiae ; the water, after it has completed its purpose, being ejected 

 through a moderately long tube, technically called the siphon. The orifice of the siphon is 

 directed towards the head of the animal, and it is by means of this simple apparatus that the 

 act of progression is effected. When the creature desires to dart rapidly through the water, 

 it gathers its six arms into a straight line, so as to 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. 



While in the act of swimming, the Argonaut's extremity of the siphon is seen projecting 

 immediately below the eye. If this action forcibly ejects water from the tube, the effect will 

 be to drive the animal rapidly in the contrary direction, i.e., from right to left. An empty 

 shell shows the partially spiral and deeply grooved keel, and an extreme tenuity of the 

 building material. 



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 furnishers 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 discs on the Argonaut's arms, these 

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



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

 each species, we must content oiirselves with a typical form of each family, and a general 

 account of its members. 



The species belonging to the family of the Octopodidse, or Eight-armed Cuttles, possess 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. A good illustration 

 of an Octopus the reader will observe in the right-hand corner of the full-page engraving 

 representing the Red Coral. 



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 swiftnegs 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 

 has 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 



