30 THE VICTORIAN NATURALIST. 



twenty-five days after oviposition, and in ten or twelve days 

 more they were discovered to have formed their Httle shells. 

 Exactly when they begin to form their shells is yet unknown. 



The body of the smaller Cephalopods occupies the whole of 

 the cavity of the shell, to which it closely corresponds in form, 

 and, as stated by Professor Owen, evidently " serves as a mould 

 upon which the shelly matter has been deposited," tlie shell being 

 gradually enlarged as the animal grows. With the larger 

 animals the body is drawn from the apex of the shell when the 

 ovarium begins to enlarge, and the unoccupied space forms a 

 chamber in which the ova are deposited. The ova consist of a 

 large bright red mass, and are attached together by a network of 

 filaments, and fill the spire of the shell. 



The Argonaut sits in its shell with the funnel turned towards 

 the keel, and swims, like other Cephalopods, by forcibly emitting 

 jets of water, which has served the purpose of respiration, through 

 its funnel, the reaction driving the animal in the opposite 

 direction. Like the Cuttle-fish also, it is furnished "with an 

 ink-bag, from which it secretes through the funnel an inky fluid, 

 which serves to facilitate its escape from danger. This is 

 frequently experienced by anyone who has captured an Argonaut 

 while gently swimming in the water, the least alarm causing it to 

 eject its inky fluid, which discolours the surrounding water, while 

 the animal suddenly sinks with its shell and swims rapidly away. 

 The ink is said to have been used by the Chinese in the prepara- 

 tion of sepia, and in Turkey and Italy the preparation of sepia 

 from the dried pigment of the ink-bags of the Cephalopods is still 

 practised. 



The oft-repeated statement that the Argonaut takes advantage 

 of fine weather to come to the surface, and spreading its 

 broad dorsal arms so as to act as sails, allows itself to be 

 propelled along by the breeze, is now discredited by all modern 

 naturalists. It was also contended by some of the earlier leading 

 Malachologists that the animal inhabiting the Argonaut shell was 

 a parasite, which, by either expelling or succeeding the original 

 owner, obtained possession. This led to a long controversy 

 among many of the leading authorities on the subject, including 

 Owen, Rang, de Blainville, Gray, and others, the result of which, 

 greatly assisted by the results of the observations made by 

 Madame Power, has been to establish the fact beyond all doubt 

 that the female Argonaut constructs her own shell by means of 

 the webbed dorsal arms. 



The male Argonaut, which is very rarely met with, differs 

 greatly from the female, being always considerably smaller ; the 

 body, not exceeding an inch in length, is not provided with a 

 shell, nor is the dorsal pair of arms developed as in the female. 

 One of the arms, the third on the left side, is, however, modified 



