66 



ma:nual of the mollusc a. 



suckers, 45 on each side ; but no branchice ; the skin contains uumerous 

 changeable spots of red or violet, like that of the argonaut.* 



According to the observations of Madame Power, " the newly hatched 

 argonaut has no shell, and is quite unlike what it afterwards becomes ; it is a 

 sort of little worm, having two rows of suckers along its length, with a fili- 

 form appendage at one extremity, and a small sweUing at the other. It might 

 be supposed to represent an extremely swall brachial appendage., fi'om which 

 the other paits were afterwards to be developed."! {KuUiker.) 

 FAMILY I. ARGONAUTID^. 



Dorsal arms (of the female) webbed at the extremity, secreting a symme- 

 trical involuted shell. Mantle supported in fi-ont by a single xidge on the 

 funnel. 



Genus Aegoxauta, Lin. Argonaut or paper sailor. 



Etymology, argonautal, sailors of the ship Ai-go. 



Synonyms, ocythoe (Rafinesque). Nautilus (Ai-istotle and Pliny). 



Example, A. hians, Soland, pi. II., fig. 1. China. 



Fig. 32. Arjonauta argo L. swimmivyA 

 The shell of the argonaut is thin and translucent ; it is not moulded on 

 the body of the animal, nor is it attached by sbell-muscles ; and the unoccu- 

 pied hollow of the spire serves as a receptacle for the minute clustered eggs;- 

 The argonaut sits in its boat with its siphon turned towards the keel, § and its 

 sail-shaped (dorsal) anns closely applied to the sides of the shell, as in fig. 32, 

 where, however, they are represented as partially withdrawn, iu order to show^ 

 the margin of the aperture. It swims only by ejecting water from its fdu- 



* Similar instances of a permanently rudimentary condition of the male sex, o<y 

 cur amongst the lowest organized parasitic crustaceans ; the males of achtheres, ler- 

 ncBopoda, tracheliaster, Sfc, are frequently a thousand times smaller than the female^ 

 upon whom they live, and from whom they differ both iu form and structure. Mr. 

 Gosse has described a similar disparity of the sexes in asplanclma. 



t An. Sc. Nat. 2 Series, vol. 16, p. 185. 



X From a copy of Rang's figure, in Charlesworth's Magazine; one-fourth the na- 

 tural size ; the small arrow indicates the current from the funnel, the large arrow the 

 direction in which the " saUor" is driven by the recoil. 



§ Poll has represented it sitting the opposite way ; the writer had once an argonaut 

 shell with the nucleus reversed, implying that the animal had turned quite round in its 

 shell, and remained in that position. The specimen is now in the York Museum. 



