384 WHALES, SEALS, AND SEA-SERPENTS 



and accepted hypothesis. But whether or no, the 

 Cetacea are mammals and not fish. The hairy coat 

 of the ordinary mammal has disappeared ; for, wet 

 and matted, without its entanglement of air, the hairy 

 covering would wholly cease to act as an efficient 

 non-conductor of heat. Its part is played by the 

 thick layer of blubber under the smooth skin, and just 

 a few hairs remain about the lips, especially in the 

 young, to remind us of the former presence of a hairy 

 coat. The blood is copious and hot, and in various 

 parts of the creature's body complex networks of small 

 bloodvessels, the " retia mirabilia," are formed to 

 hold the plentiful supply. The hind-legs have dis- 

 appeared to outer view ; but, within the body, rem- 

 nants of the pelvis, thigh-bones, and sometimes even 

 of the leg-bones, are still to be found. The fore-limbs 

 are in many ways peculiar : the arm-bone is extremely 

 short, sometimes almost as broad as it is long ; its 

 great round head moves freely on the shoulder-blade, 

 but elsewhere the limb has little or no freedom, the 

 fingers being bound together by sinew and skin, and 

 the flipper moving all of a piece. The flippers are 

 usually small, but sometimes of great length, as in 

 the Caaing Whale (Globiocephalus) and the Humpback 

 (Megaptera) ; and it is not by their means that the 

 creature swims, but by the sculling action of the flukes 

 of the mighty tail, the flippers being in all probability 

 mainly for the purpose of maintaining equilibrium 

 in the water, for keeping the animal on an even keel. 

 While all other mammals soever have in the fingers 

 and toes the same number of joints that we have, in 

 the whales these numbers are always exceeded ; and 

 sometimes (Globiocephalus) the finger has twenty 

 joints or more, so that the limb has a great resemblance 

 (however that may have been brought about) to the 



