218 NATURAL HISTORY OF OUR SHORES 



from which the tentacles arise is the mouth (Fig. 94), and 

 this is furnished with a horny, parrotlike beak, which can 

 be protruded or retracted. 



The under side of the body is in the form of a flap, like 

 the outer half of a folding, india-rubber tobacco pouch. 

 Within the cavity thus formed are the two gills and an 

 ink bag for Octopus, like its allies, has this protective 

 arrangement, the use of which we shall presently see 

 and pointing forward in a median line is the Syphon, 

 a funnel-shaped arrangement with the small end out- 

 wards, and formed of thin, strong membrane. At each 

 inspiration water is taken in through the opening of 

 the flap or mantle fold, and in expiration the water is 

 forced through the tube in a strong stream, the mem- 

 braneous edge of the tube closing during the act of in- 

 spiration. Tn a large specimen the diameter of the syphon 

 is about half-an-inch. It is through the same tube that 

 the ink is expelled when occasion requires. 



The skin of the octopus is like damp kid leather, 

 and is very elastic. At times it lies smooth and even, but 

 can also be raised in little papillar eminences, sometimes 

 in ridges, like little mountain chains. A tall papilla is in- 

 variably raised, hornlike, just over each eye. 



These elevations are only shown when the animal is 

 quiescent, and considers itself in security. 



The coloration of the octopus is very remarkable : I do 

 not think any animal can make such a series of colour 

 variations so rapidly. 



When at rest and unexcited the general tint is purple 

 brown, but there is a constant series of slight changes 

 grey, brown, purple passing, wavelike, over it. When 

 highly content, as after a meal, and perched, as it is fond 

 of perching at times, upon an eminence, the papillaB are 

 erected, and these are always of an orange colour. 



Oftentimes the whole body will be marked off in irre- 



