MOLLUSCA CEPHALOPODA. 



233 



shown in Fig. 1*23* b, we find that it is formed of a 

 great number of long slender pieces, resembling 

 teeth closely set together, and extending from the 

 inner margin of the cartilaginous ring, in the form 



of converging radii, to within a short distance of 

 the centre, where they leave a circular aperture. 

 In the flattened state of the sucker, this aperture 

 is filled by the projecting part of a softer substance, 

 which forms an interior portion, capable of being 

 detached from the flat circle of teeth, when the 

 sucker is in action, and of leaving an intervening 

 cavity . The form of this cavity is exhibited in Fig. 

 c, which represents a perpendicular section of the 

 whole organ, and where the central portion, or 

 principal mass of the sucker is drawn away from 

 the circular disk, the inner margin of which appears 

 like a row of teeth. It is evident that by this 

 mechanism, which combines the properties of an 

 accurate valve, with an extensive cavity for pro- 

 ducing rarefaction, or the tendency to a vacuum, 

 the power of adhesion is considerably augmented.* 



* The description I have here given is the result of my own ex- 

 amination of a large Octopus, which I had lately an opportunity of 

 dissecting: and the annexed figures 123*, a, b, c, are copied from 

 drawings I made on that occasion, a represents the sucker in its 

 usual form when not in action : b shows the sucking surface fully 

 expanded : and c is a section of the whole, which had become some- 

 what flattened by the operation of dividing it. 



