332 



MOLLUSCS. 



SHELL OF FEMALE ARGONAUT. 



surface of the water with the coiled part of the shell upwards, a small portion being 

 above the surface, to which the aperture was at right angles or inclined at an angle 

 of 45°. It appeared calm and not subject to agitation like the octopus. It 



remained perfectly immovable, for no menace or 

 excitement appeared to affect this appearance 

 of tranquillity. Like the octopus, it exhibited 

 chameleon -like changes of the skin, but not so 

 rapidly or with such intensity as that animal. 

 During all the time the specimen lived, all the 

 arms, which have two rows of suckers, were 

 kept within the shell, except the expanded 

 posterior median pair. These, however, were 

 also sometimes drawn within. Four of the 

 arms were bent upwards, four downwards, 

 leaving the mouth with its parrot-like beak 

 exposed in the middle of their bases. Between 

 the lower or ventral pair of arms the funnel was 

 protruded, by means of which it propelled 

 itself backwards. This specimen was not seen 

 either to walk or swim with its arms; but 

 other observers state that the creature walks 

 or crawls along the bottom like a gastropod, 

 by means of the non-expanded arms, carrying the shell above its body. The eye 

 is round, bordered with black, and the circular pupil is also black. 



The shell is supposed to be secreted chiefly by the palmate arms, aided by the 

 mantle investing the body. It is developed some time after the birth of the argonaut, 

 and a female has never been seen with a shell before it had attained about an 

 inch in length. The male argonaut is very different to the female, and much 

 smaller, being only about an inch in length. It resembles an ordinary octopus in 

 having neither palmate arms nor shell. The arms are tapering and alike, excepting 

 the third on the left side, which is specialised. This at certain times, having 

 passed through various stages of development, is cast off, and attaches itself to the 

 female, living a free and independent life for a considerable period. The eggs are 

 small, numerous, and connected together by a network of filaments. They are 

 deposited far within the shell towards the convoluted portion, and are practically 

 in contact with the posterior part of the body of the parent. The shell therefore 

 serves, not only as a retreat for the argonaut herself, but also as a nest for the eggs, 

 and possibly as a nursery for the young. Very little is known with regard to the 

 food of the argonaut. As its habits are very similar to those of the octopus, it 

 seems probable that it may feed upon molluscs and crustaceans, which it might 

 capture when crawling at the bottom of the sea. A captive specimen was fed with 

 small live fish, which it ate with avidity. About eight species are recognised, 

 which have a world-wide distribution, occurring in all tropical and warm latitudes. 

 The shells of the different species are all of a white colour, and exhibit two distinct 

 types of surface ornamentation, the one consisting of simple, smooth, radiating 

 wavy ribs, the other in which these ribs are more or less broken up into nodules or 



