470 



ZOOLOGY 



fashion so judicial as to win acceptance by all. Charles Dar- 

 win was born in Shrewslsury, England, in 1809; his uncle, 

 Erasmus Darwin, had written a theorj- of e\'olution in metric 

 form. After having studied in Edinburgh and Cambritlge, 

 Charles Darwin, at the age of 22, accompanied the ship 



Beagle on a five years' scientific 

 expedition around the world. 

 On this trip he made studies on 

 the chstribution of animals in 

 space and time, and published 

 a fascinating Ijook on them. 

 These studies led him, on his 

 return, to collect facts which 

 might Ijear on the origin of 

 species. In 1859 Darwin jau))- 

 lished his book entitled " The 

 Origin of Species through Nat- 

 ural Selection." Besides the 

 general argument for evolution, 

 he proposes the special hypothe- 

 sis of selection to account for it. In ever}' species many 

 more individuals are produced in each generation than 

 can survi\'e. In this weeding-out process those individuals 

 that in any way peculiarly fit the conditions of life will 

 be more apt to survive than the less fit; thus the fact of 

 adaptation is accounted for, and, whene^'er the en\'ironment 

 changes, a change in the species tends to occur. Darwin was 

 inclined to beheve that the changes in successive generations 

 would l)e always shght, but the experiments and oljservations 

 of the Dutchman De Vries ("The JNIutation Theory" 1901- 

 1903) make it seem proI)al)le that the progressive steps are 



Fig. 421. 



Hugo de \'ries. 



