'S^S Natural ithtory of Molluscous Animals : — 



bed arms at the same instant." * Mr. Cranch likewise informs 

 us, that the parasitical and finless Oc5'thoe swim freely when 

 out of their shell, having, as he adds, all the actions of the 

 common Octopus of our seas. These quotations, we pre- 

 sume, will be deemed conclusive ; and, from the first, we learn 

 by what organs they swim. It is by means of the tentacula 

 just raentit)ned ; long tapered organs, which encircle the head 

 as with a crown, are capable of being inflected in every direc- 

 tion, and, in this tribe, are edged with a web-like membrane, 

 serving to unite them all together towards their origins. 

 Desmarest has observed the Octopodiae to have another mode 

 of progression, and one very unusual amongst animals ; viz. 

 by rolling over upon themselves with great velocity, and 

 without fixing themselves by their tentacula. f 



Some :j: of this tribe, as I formerly hinted, take possession 

 of the shell of the paper nautilus (Argonauta A'rgo), and make 

 it their boat; a purpose for which it is admirably fitted by its 



129 e^s&pj^ja^®**!^ lightness and navicular 



form. It is said that 

 the (Sepia lays over 

 each side of the shell 

 three of its tentacula, 

 which it uses for oars, 

 and raises up other two 

 dilated at their ends 

 by a thin oval mem- 

 brane, which fancy may 

 compare to a sail, and 

 which serve the pur- 

 pose of one. Having, 

 by a process yet unexplained, risen to the surface, this pirate 

 sailor thus plies his vessel with oar and sail ; but ever timorous 

 as a guilty thing, he shrinks within on the least alarm, and 

 sinks again into his port, the deep. (Jig, 129.) 



" Light as a fiake of foam upon the wind, 

 Keel upward from the deep emerged a shell, 

 Shaped like the moon ere half her horn is fill'd ; 

 Fraught with young life, it righted as it rose. 

 And moved at will along the yielding water. 

 The native pilot of this little bark 

 Put out a tier of oars on either side. 

 Spread to the wafting breeze a twofold sai', 



* Edin. Phil. Journ., xvi. 313. 

 f Blainville, Man. de Malacologie, p. 149. 



:j: Bosc says that more than one species occupy the shell of the Argo- 

 nauta A'rgo. Hist. Nat. dcs Vers., i. p. 50. 



