THE EXTERNAL FORM OF WHALES g 



lamprey with a pair of skin folds in the neighbour- 

 hood of the vent, which are believed by some to 

 represent a pair of otherwise missing hind limbs. 

 Apart from these folds there is no trace of limbs, no 

 skeletal elements that is to say. 



Plausible though such a derivation of the flukes of 

 the whale may be, there are arguments which seem 

 to be absolutely fatal to their entertainment. The 

 tail (of Phoccena communis), when it first appears, is 

 a prolongation of the body sharply marked off from 

 the body, and precisely, so far, like the tail of a 

 typically-tailed and terrestrial mammal. This tail has 

 at first practically no lateral flanges. When these 

 put in an appearance they are obviously lateral ex- 

 pansions of the integument, and the tail has a 

 diamond-shaped outline ; it is indeed not unlike that 

 of a Manatee in general shape. 



It is interesting to note this fact, for the Manatee 

 is clearly an animal whose ancestors were less re- 

 motely terrestrial in habit. (See p. 90.) Finally, the 

 characteristic flukes of the adult are acquired. But 

 the argument which seems to conclude the matter 

 is that in this same porpoise, coincidental^ with the 

 appearance of the lateral flanges of the tail (the 

 supposed hind limbs, be it remembered), distinct 

 traces of those same hind limbs are visible in their 

 proper place, that is to say, considerably in front of 

 the tail. 



If a further argument in the same direction be 

 wanted, it is afforded by the analogy of the Ichthyo- 

 saurus. These aquatic reptiles have been lately 



