24 
PROOFS OF EVOLUTION. 
gradual changes, from the simplest beginnings up 
to their present complex state. New and ever- 
changing environments have brought correspond¬ 
ing modification of the organs or parts. Those 
no longer needful, shrunk to rudiments, finally 
disappeared altogether. Those needful and used 
were strengthened along their several lines of 
growth, until we have to-day all the wonders of 
form and function. 
Nature never begins her work de novo , for her 
adaptive genius is so great that she can transform 
the old into the new. When she wanted to make 
a landsman of a fish, she did not give him a new 
pair of legs at once, but left him to utilize his fins 
for that purpose as best he could. Of course, he 
made bad work of it at first; but as he was left 
in the hard grip of necessity it was Hobson’s 
choice. As he was often left on shallow, muddy 
shores by receding tides, he began to work his 
fins more vigorously, until finally, after many 
generations, in spite of a round of fatal failures, 
some of his kind succeeded in adapting their fins 
to this new use. The mud-fish of India, the 
Brazilian doras, and certain catfish of tropical 
America, take journeys of considerable length 
