14 THE STORY OF FISH LIFE. 



sence, in many cases, of a dorsal fin, and the 

 peculiarly fin-like fore-limbs render this mistake 

 a very natural and quite pardonable one. But 

 it is not a fish, because it suckles its young like 

 all the rest of the mammalia, consequently it is 

 with this group that we must place the whale 

 and its allies. But there are yet other reasons 

 which forbid us to regard the whale as a fish, 

 and compel us to recognise it as a mammal. If 

 we examine a skeleton of one of these creatures 

 we shall find it differs fundamentally from that 

 of the fish, and agrees closely with that of the 

 mammalia. The points wherein it differs from 

 the type all show undoubted adaptation to and 

 specialisation for particular mechanical needs. 

 Thus the fore-limb is obviously a mammalian 

 fore-limb, which has undergone certain changes, 

 converting it into a paddle for swimming pur- 

 poses. The whale, being poised in the water 

 like a fish, has ceased long since to need support 

 from its sometime functional legs. The fore- 

 limbs being useful have been transformed into 

 paddles, the hind-limbs not being required have 

 disappeared long ago, leaving only slight traces 

 of the hip-girdle imbedded in the muscles of the 

 body. The structure of the skull, backbone, 

 ribs, breastbone all tell the same tale ; so do the 

 brain, heart, lungs, and other viscera all point 

 emphatically, beyond all possibility of doubt 

 whatsoever, to the irresistible conclusion that 

 the whale and its allies are not fish but mammals. 

 The seals point the way in which this peculiar 

 modification has come about, being half-way 

 stages between the typical walking mammal and 



