I 



CHAPTER XXXVI 

 THE RESULTS OF EVOLUTION 



Adaptation. — The current of life, as it has flowed 

 through the ages, resembles a mighty river, or better, 

 perhaps, the slow-moving glacier, which at varying dis- 

 tances from its source breaks up or evolves into numerous 

 branches. And in much the same manner that the glacier 

 fits into the inequalities of its bed, the various species of 

 animals and plants fit into or are adapted to their sur- 

 roundings. This is the great outstanding characteristic 

 of living things. Furthermore, adaptation does not stop 

 with the organism as a whole. On the contrary, every 

 system, organ, tissue, cell and the elements of the cell 

 itself are all adapted parts of the vital machine. The 

 results of evolution therefore are largely summed up in 

 the one word, adaptation. 



Convergent Adaptations in Animals. — Viewed in 

 its broader aspects, one striking feature of adaptation 

 among organisms is the so-called convergence or parallel- 

 ism of form. That is to say, many species of animals and 

 plants, surrounded by essentially the same conditions,bear 

 a superficial resemblance to each other. The whale for 

 example has been called a fish since the days of Jonah. 

 In reality this is a case of convergence whereby a hairy, 

 warm-blooded vertebrate, or mammal, has evolved a form 

 of body adapted for cleaving the water with the least 

 possible resistance. Its resemblance to cold-blooded 

 fish is entirely superficial. The same is true of the ex- 

 tinct fish-like reptiles, which long ago inhabited the sea. 



Another familiar example of convergence occurs among 

 the birds, bats, certain ancient reptiles and to a less ex- 



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