ARGONAUT. BELLEROPHON. 349 



Madame Power (who has kept a number of these animals in a 

 kind of cage inclosed from the sea in the bay of Messina), that 

 the shell increases regularly with the growth of the animal ; and 

 that the Mollusk possesses the power of repairing the shell when 

 injured, in a manner corresponding to its original formation ; 

 whence no reasonable doubt can exist, that the Argonaut is the 

 real construction of it. 



891. Of the eight arms of the Argonaut, six taper gradually 

 towards the extremities ; but two are expanded into wide mem- 

 branous flaps. From very early times, this animal has been 

 reputed to swim on the surface of the sea, using its arms as oars, 

 and spreading these expanded membranes as sails, so as to be 

 wafted along by the wind. But it is now known by accurate 

 observation of the living animal, that this is altogether a fiction 

 (though an interesting one) ; and that the expanded membranes 

 are spread over the sides of the shell, meeting along its keel or 

 edge, and completely inclosing it. It is by these, indeed, rather 

 than by the surface of the body itself, that the calcareous 

 secretion is poured out, for the enlargement or reparation of 

 the shell. It will be observed that there is a double row of 

 suckers along the edge of each of the expanded arms ; and by 

 these suckers they are held in close contact with each other along 

 the keel of the shell. When the animal withdraws its whole 

 body into the shell, the exterior of the latter is about half 

 uncovered, the expanded arms also being partly drawn in. By 

 the action of the arms, the Argonaut can swim backwards in 

 the same manner as other Octopi ; and it can also creep along the 

 bottom of the sea. There is a fossil genus, Bellerophon, abundant 

 in the mountain-limestone formation ; which, from the charac- 

 ters of its shell, is regarded as nearly allied to the Argonaut. 



892. The Decapod family, which, besides the eight ordinary 

 arms, has two longer and slenderer ones, presents many points 

 of approach to the Tetrabranchiate Order. This affinity is indi- 

 cated, not merely by the increased number of the external arms, 

 but by their smaller size in proportion to the body, by the 

 frequent development of a second row of small tentacula within 

 the others, and by several internal characters, especially the 



