288 PHILOSOPHICAL TRANSACTIONS. [aNNO 1758. 



oval bag issuing from it b, and the pipe rising upward towards the arms c. Fig. 

 4 shows the polypus with its transverse opening and the pipe rising from it, but 

 without the oval bag ; it is figured thus by Rondeletius and G^sner, and the 

 specimen at the British Museum has also this appearance. It is here shown 

 with the arms extended forwards, k is a magnified figure of one of the aceta- 

 bula or suckers ; of which there are 2 rows on each arm of this polypus, as before 

 described. 



Mr. Needham, in his description of the suckers of the calamary, (which he 

 had many opportunities of examining while alive, and whose mechanism is pro- 

 bably the same as in those of our polypus) informs us, ' that the action of the 

 suckers depends partly on their shape, which, when they are extended, resembles 

 nearly that of an acorn-cup, and partly on a deep circular cartilaginous ring, 

 anued with small hooks, which is secured in a thin membrane something trans- 

 parent, by the projection of a ledge investing the whole circumference about the 

 middle of its depth, and not to be extracted without some force. That each 

 sucker is fastened by a tendinous stem to the arm of the animal: which stem, 

 together with part of the membrane that is below the circumference of the carti- 

 laginous ring, rises into and fills the whole cavity when the animal contracts the 

 sucker for action. In this state whatever touches it is first held by the minute 

 hooks, and then drawn up to a closer adhesion by the retraction of the stem 

 and inferior part of the membrane, much in the same manner as a sucker of 

 wet leather sustains the weight of a small stone.' Vide Microscopical Disco- 

 veries, p. 22. 



M shows one of the cartilaginous rings armed with small hooks. The ring 

 this is drawn from was taken out of a large sucker of a larger polypus. By these 

 suckers the polypus can fix itself to rocks, and prevent its being tossed about in 

 storms and tempests ; but their principal use must doubtless be to seize and hold 

 its prey: and to this purpose they are most admirably adapted; for when they 

 are all applied and act together, unless the polypus pleases to withdraw them, 

 nothing can get from it whose strength is insufficient to tear off its arms. Some- 

 thing like these suckers is found by the microscope in the minute fresh-water 

 polype, by which it is able to bind down and manage a worm much larger and 

 seemingly stronger than itself. In like manner the Stella arborescens, which may 

 also be called a polypus, though it has not suckers, yet by the hooks along its 

 arms, and the multiplicity of their branchings, which have been counted as far 

 as 80,CXX), it can, by spreading its arms abroad like a net, so fetter and entangle 

 the prey they inclose when they are drawn together, as to render it incapable of 

 exerting its strength : for however feeble these branches or arms may singly be, 

 their power united becomes surprizing. And we are assured Nature is so kind 

 to all these animals, that if in their struggles any of their arms are broken off. 



