120 THE CEPHALOPODS — THEIR MOTIONS. 



them as it is to the flying-fish, — being, by the vigour of their 

 strokes, sometimes raised some feet above the level of the 

 water. Thus Colonel Sykes mentions, that several speci- 

 mens of Loligo sagittata leaped on board the vessel in which 

 he was returning from India, while the wind was light and 

 the sea calm.* In some species their motions are greatly 

 assisted by the broad membranes that fringe the feet and 

 connect them together at their base. Such membranes are 

 found on the two inferior pairs of feet in the Loligopsis ve- 

 ranii, — a species to which I shall call your attention more 

 particularly hereafter. The Sepias aid and regulate their 

 motions by the power they have of introducing air at option 

 into the numerous cells of the backbone, and thus at will 

 varying their proportionable weight to the sea in which they 

 live.-j-- In the finless Octopods the feet, which are all winged 

 with a membrane, become the sole organs of natation ; for 

 though Lamarck has chosen to maintain that this family can 

 only trail themselves along the bottom of the shore they 

 inhabit by means of their arms, J we know very well that 

 they are excellent swimmers, § propelling themselves by 

 repeated strokes of their members, used much in the fashion 

 that a frog uses its legs. Thus Professor Grant, when 

 describing the Octopus ventricosus, says, — "The animal 

 swam several times hurriedly across the basin, always with its 

 posterior extremity forward, by repeatedly striking forward 

 the whole of its webbed arms at the same instant." Mr. 

 Cranch likewise informs us, that the finless Ocythoes 

 swim freely when out of their shell ; having, as he adds, 

 all the actions of the common Octopus of our seas. The 

 Octopods, however, do walk with equal ease, dragging their 

 body, which is round and proportionably small, along the 

 ground at the rate, it has been ascertained, of not less than 

 seven feet in a minute. Should they wish to accelerate their 

 pace, they inflate their body until it resembles a distended 

 bladder ; when, leaving go all hold and casting themselves 

 forward, they roll over and over with great velocity, and 

 often effect an escape which would otherwise have been 

 impossible. j( 



* Proc. Zool. Soc. 1833, pt. i. p. 90. 



t Good's Study of Medicine, iv. 424. 



J Anim. s. Vert. vii. 583, 656. 



§ Cuvier, Mem. i. 3. 



|| Edinb. Phil. Journal, xvi. 313 See also Darwin's Journal, iii. 6. 

 Yet Mr. Couch says of Octopus vulgaris, " It is scarcely capable of swim- 

 ming ; but it is a common amusement of boys to cause it to climb up the 

 ascent of a pole or mast." — Cornish Fauna, 82. 



IT Blainville Man. de Malacologie, 149. The Naturalist, i. 190. 



