WHALES AND SEALS 87 



plain and obvious likenesses. There are others, which 

 a closer study and comparison of the two groups 

 bring to light. The flippers have no nails in the 

 whales, though in the foetus traces of the structures 



o 



have been discovered by Kiikenthal. In the sea-lions 

 the nails, though still recognisable, are exceedingly 

 small, and not of the faintest use for scratching or 

 any other nail function. This is not always the case 

 with the true seals ; in Phoca, the seals of our coasts, 

 there are well-developed claws on the hand, but on 

 the other side we have the Antarctic genus, Ommato- 

 phoca, with the fore limbs furnished only with quite 

 rudimentary nails. The nails, therefore, may be fairly 

 said to be disappearing in all these animals. 



Another feature in which there is a functional re- 

 semblance between whales and seals is in the hind 

 limbs. Considering that the latter are merely re- 

 presented by tiny rudiments in the whales, the 

 comparison may seem at first sight to be a little 

 ridiculous. But there is, as has been observed, a 

 functional likeness in spite of this obvious dis- 

 similarity. The hind limbs of the seal tribe play 

 the part of a tail ; they are extended beside the tail 

 and act precisely as do the flukes of the tail in the 

 whale ; it is by their means chiefly that the creature 

 is propelled through the water. In the one group 

 the unnecessary hind limbs have nearly disappeared 

 altogether ; in the other they have, as it were, become 

 part of the tail. It is evident that an aquatic beast 

 does not need the usual two pairs of limbs ; the fact 

 is shown also among fishes, but again in a different 



