Cephalopoda ■■ 



-MOLLUSCA.- 



-Argonauts. 



313 



abundant in the Mediterranean, as well as the Atlantic 

 and Indian oceans, the best known species. The shell 

 of this species is a very beautiful object, and the favourite 

 of poets and artists of all ages. As Dr. Johnston 

 observes, it is the original whence artists have derived 

 many a pretty design for the car in which the sea-born 

 Venus is made to ride the ocean, and which "sportive 

 dolphins drew." It is the " little Nautilus " of Pope, 

 who as a poet improved upon the pretty picture of 

 the animal given by Aristotle, who described it as 

 floating on the surface of the sea in fine weather, and 

 holding out its sail-shaped arms to the breeze. Pliny 

 endorses Aristotle's notion of its raising its webbed 

 arras and spreading them out as a sail ; and the poet 

 Montgomery, in his Pelican Island, has since his time 

 " married it again to immortal verse" : — 



*' Light as a flake of foam npon the wind, 

 Keel upward, from the deep emerged a shell, . 

 Shaped like the moon ere half her horn is filled ; 

 Fraught with young life, it righted as it rose. 

 And moved at will along the yielding water. 

 The native pilot of this little hark 

 Put out a tier of oars on either side, 

 Spread to the wafting breeze a twofold sail, 

 And mounted up and glided down the billow 

 In happy freedom, pleased to feel the air 

 And wander in the luxury of light." 



The movements of this beautiful mollusc, however, 

 are now better known, and have been stripped of the 

 fable and poetry which enveloped them. The little 

 sailor sits in its boat with its siphon turned towards the 

 keel, and its sail-shaped dorsal arms closely applied to 

 tlie sides of the shell — fig. 210. It swims by ejecting 



water from its funnel or siphuncle, and like the rest of 

 the Cuttle-fishes, the motion is backwards, the shell 

 being driven in that direction by the recoil caused 

 by the sudden and forcible expulsion of the water for- 

 wards. Its motions, however, are not confined to 

 swimming, as it crawls at the bottom of the water in a 

 reversed position, carrying its shell over its back like 

 a snail. 



These creatures are very shy and timid. " During 

 calm weather," says Madame Jeannette Power, " and 

 in quiet water, if not feeling themselves observed, they 

 make a parade of their many beauties, rowing with full 

 sails tinged with beautiful colours, and resting the 

 extremities of their sail-arms on the two sides of the 

 shell, or embracing the shell with them. It is then 

 that their different movements and habits may be 

 observed ; but I was obliged to act with the greatest 

 caution in order to enjoy this spectacle, for the creatures 

 are extremely suspicious, and no sooner find them- 

 selves observed than they let themselves fall to the 

 bottom, and do not rise again for many horn's." Mr. 

 Arthur Adams, during the voyage of the Samaranrj, 

 had frequent opportunities of observing two species of 

 Argonaut with their living inhabitants, and corrobo- 

 rated two facts with regard to their history. He 

 observed "that the female Argonaut can readily dis- 

 engage herself from the shell, when the velamentous 

 arms become collapsed, and float apparently useless 

 on each side of the animal ; " and ascertained from 

 experiment " that she has not the ability, or perhaps 

 the sagacity, to enter her nest again, and resume the 

 guardianship of her eggs." He was satisfied also 



Fig. 210. 



Swimming Argonaut, 



"that the thin shell of the Argonaut is employed by the 

 female as a safe receptacle in which to deposit her 

 eggs;" for he dissected a specimen of A. tuberculosa 

 {A. nodosa) that was taken firmly embracing the shell, 

 which contained a large mass of eggs occupying the 



discoidal portion of the chamber and the posterior por- 

 tion of the roof. The eggs he describes as being very 

 numerous, and united together by a delicate, glutinous, 

 transparent, filamentous web, and suspended to the 

 body whirl of the spire. 



Sub-order II.— DEC APOD A (Decapods). 



In this snb-order the body of the animal is elongated, 

 oblong, or cylindrical, and always provided with a pair 

 of fins. The mantle is supported by a fleshy band, or 

 Vol. II. 



by cartilaginous buttons and loops; and the body is 



strengthened in the middle of the back by an internal 

 shell, which is longitudinal and either horny or cal- 



2 R 



