346 OCTOPUS OR POULP. 



Naturalists ; who were quite unacquainted with the animals to 

 which the name is now restricted. (Indeed this name was first 

 conferred on the Hydra and its allies, on account of their simi- 

 larity in form, and in the position of their prehensile arms or 

 feet, to the animal previously known under that appellation.) 

 The common Poulp has arms six times the length of its body ; 

 and each of these is furnished with 120 pairs of suckers. Every 

 sucker is composed of a circular adhesive disc composed of a 

 muscular membrane ; this has a thick fleshy circumference, and 

 presents a number of lines radiating towards the circular orifice 

 of an inner cavity, situated beneath the central part of the disc. 

 In this cavity is a moveable circular piston ; which, when the 

 sucker is not in action, appears level with the circular aperture; 

 but which, when the disc is closely applied to any object, is 

 strongly drawn back, so as to increase the size of the cavity and 

 produce a vacuum in it ; forming, in fact, an air-pump of the 

 most precise and beautiful construction. When the animal 

 releases its hold, it relaxes the muscles that drew back the 

 piston ; and the vacuum is then made to cease. The whole 

 apparatus might be compared to a boy's leather-sucker, with an 

 exhausting syringe fitted to its centre. 



888. It may be noticed, as a curious example of reflex action, 

 that the nervous trunk supplying .each arm of the Octopus, is 

 furnished with a series of ganglia, corresponding in number and 

 position with the suckers. A part of the trunk passes over the 

 whole series of ganglia without entering them, precisely as in 

 the case of the ventral cord of the Articulata ( ANIM. PHYSIOL. 

 442) ; and this sends branches into each sucker, so as directly 

 to convey to them the influence of the cephalic ganglia, and thus 

 to cause them all to contract at the will of the animal. On the 

 other hand, each sucker receives nervous filaments from its own 

 ganglion ; and may be made to contract, when stimulated to do 

 so, by the contact of a solid substance, even though the arm is 

 entirely separated from the body. Hence, when a Cuttle-fish 

 has fixed itself upon any animal, it may be cut into pieces with- 

 out the suckers relaxing their hold ; since the muscles of every 

 sucker are called into action by the reflex properties of its own 



