60 CEPHALOPODA, 
gliding by. ‘The instant that the Cuttle feels the 
contact, instinctively, and with the speed of light- 
ning, it retracts the fleshy piston; a vacuum is 
thus created, and the edges of the disk are pressed 
against the surface of the victim, with a force equal 
to the weight of the water that is above it, added 
to the weight of the atmosphere. If need be, as 
when the victim makes strenuous efforts to escape, 
STRUCTURE OF SUCKER. 
the vacuum, and consequently the adhesion, is in- 
creased by the withdrawal of the membranous disk. 
This apparatus, powerful as it is, is but one out 
of a thousand instruments of the same kind with 
which the animal is furnished. Our common 
Poulpe ( Octopus vulgaris) has eight tentacular arms, 
and every one of these carries one hundred and 
