298 



CEPHALOPODA. 



r%'m^ 







their activity and the various means that they possess 

 of seizing and of holding then- prey, are exceedingly 

 destructive to fishes and crustaceans around our 

 coasts. 



Their prehensile arms are, in the greater number of 

 species, provided with suckers, called " Acetabula," 

 _ that act like . cupping- 

 glasses. The mechanism 

 for producing adhesion 

 by means of these Avon- 

 derful organs is extremely 

 curious. From the mar- 

 gin of each cup muscular 

 fibres converge towards 

 the centre, at a short dis- 

 tance from which they 

 leave a circular aperture ; 

 behind this is a false 

 floor that can be raised, 

 like the piston of a 

 syringe, and thus produce 

 a complete vacuum with- 

 in the cup. So perfect 

 is this mechanism that, 

 while the piston continues 

 raised, it is easier to tear 

 away the sucker from the arm than to release its hold, 

 but as soon as the muscular effort raising the piston 

 ceases, the vacuum produced by its retraction is in 

 an instant destroyed, and all the suckers detach 

 themselves.* 



Few spectacles are more wonderful than that pre- 



* The tenacity of the gripe of the Cephalopod was fiilly appre- 

 ciated by Homer, but the beauty of liis simile has been but little 

 understood by his translators : — 



" As when the Cuttle-fish enforced forsakes 

 His rough abode, with his adhesive cups 

 He gripes the pebbles still ; 

 So he, Ulysses, with his lacerated grasp, 

 The crumbled stone retained, when from his hold 

 The huge wave forced him, and he sank again." 



Homer's Odyss. Book V. 



Fig. 238.— STKUCTXIRE OF SUCKERS 

 OF CUTTLB-FISH. 



