xxvi STUDIES IN THE EVOLUTION OF ANIMALS 



I confess that this theory which considers the fish-like mammals 

 as having descended from land mammals which took to aquatic 

 habits does not seem to me satisfactory. Zoologists would appear 

 to have conceived a roundabout way of evolving a Whale. The 

 fish is made first to evolve a land mammal, and then this takes to 

 the water again and gets rid of its hind-legs. It seems clear to me 

 that if the fish proper could evolve a land mammal, it could also 

 evolve a water mammal, without the necessity of going through this 

 roundabout performance. If a bird could lose its fore-limbs on 

 land, it would appear that a Whale could lose its hind-limbs in the 

 water. 



This notion presupposes the possibility of land mammals 

 evolving from fishes, and the impossibility of water mammals 

 evolving from the same fishes. And all this in face of all we know 

 about the Ichthyosaurs and Plesiosaurs, with their dwindling hind- 

 limbs ; in face of the shore and land fishes hopping about on their 

 pectoral fins on land, so that they are difficult to catch ; in face of 

 the fact that certain fishes proper can breathe either by gills or by 

 lungs, according to circumstances ; and in face of the fact, which 

 every one knows, that the Tadpole is first fish-like, and then evolves 

 arms and legs without getting out of the water. 



Are we so sure, in spite of ' agreement among zoologists,' that 

 the Whales are degenerated land animals, and that land animals are 

 not further evolutions of fish-like animals which have taken to life 

 on dry land, while the Whale, evolving from the same fish-plane, 

 remained a water mammal ? 



In the amphibians alone we have ample evidence that a fish- 

 like vertebrate can grow arms and legs without leaving the water ; 

 and in the Ichthyosaurs we have again ample evidence that the 

 hind-limbs were already undergoing degradation, and that in the 

 Plesiosaurs both the hand and foot had become degraded to 



