756 THE POPULAR SCIENCE MONTHLY, 



mated "mimicry." That cuttle-fishes possess such a power is well 

 known. The hue of an octopus may so closely resemble that of the 

 rock to which it attaches itself, that the observer can with difficulty 

 say which is rock and which is animal. A flounder's color is in 

 the same way assimilated to the sand on which it rests, although 

 in the fish the alteration of color seen in the cuttle-fishes is not rep- 

 resented. 



The manner of production of the changes of hue and play of 

 " shot " colors in the cuttle-fishes is really analogous to that whereby 

 the famed chameleons effect their alterations of hue. 



The locomotion of the cuttle-fishes forms a point of interest in con- 

 nection with their general structure and physiology. Any one who 

 has attentively watched the movements of an octopus in its tank must 

 have been struck by the literally acrobatic ease with which it accom- 

 modated itself to the exigencies of its life and surroundings. In their 

 lithe, muscular, and flexible arms, the cuttle-fishes possess an apparatus 

 which is equally serviceable for the capture of prey, and for walking 

 mouth downward that is, in their structurally natural position. 

 They possess, likewise, the power of swimming upper side forward 

 or popularly stated " backward " by means of the jets of water 

 which, by forcible contractions of the muscular mantle-sac, are pro- 

 jected from the tube or " funnel " situated on the hinder face of the 

 body. These jets d^eaii consist of the effete water which has been 

 used in breathing, so that the act of expiration and the effete water 

 of respiration together become utilized, in the economical wisdom of 

 nature, as a means of propulsion. The mysterious backward flight of 

 an octopus through its tank (Fig. 1), when, detaching itself from its 

 hold on the rock, it swims gracefully and swiftly through the water, 

 is effected in the manner just described. This form of hydraulic ap- 

 paratus, imitated in experiments in marine engineering, serves but to 

 strengthen the wise man's adage concerning the utter lack of novelty 

 in terrestrial and mundane things. 



It is equally interesting to note that some of the squids or loligos 

 named popularly " flying squids " appear to be able to rise from 

 the surface of the sea and to spring into the air after the fashion of 

 the flying-fishes. Instances are mentioned of the flying squids having 

 occasionally landed themselves on the decks of ships in their atmos- 

 pheric leaps. 



The " arms " or " feet " demand, however, a somewhat detailed 

 mention, on account of their armature. In all cuttle-fishes, save the 

 exceptional pearly nautilus, the arms are either eight or ten in number, 

 and are provided with acetabular or " suckers." Those cuttles in 

 which ten arms are present and of these the squids and sepias form 

 good examples have two of these appendages produced beyond the 

 remaining eight in length. The " suckers " (Fig. 2, a), which consti- 

 tute a most noteworthy armament of the arms, are borne on short 



