A HALF-CEXTURY OF SCIENCE. 67 



begin. Fifty years ago it was the general opinion that animals and 

 plants came into existence just as we now see them. We took pleas- 

 ure in their beauty ; their adaptation to their habits and mode of life 

 in many cases could not be overlooked or misunderstood. Neverthe- 

 less, the book of Nature was like some richly illuminated missal, writ- 

 ten in an unknown tongue ; the graceful forms of the letters, the 

 beauty of the coloring, excited our wonder and admiration ; but of 

 the true meaning little was known to us ; indeed, we scarcely realized 

 that there was any meaning to decipher. Now glimpses of the truth 

 are gradually revealing themselves ; we perceive that there is a reason 

 and in many cases we know what that reason is for every difference 

 in form, in size, and in color ; for every bone and every feather, almost 

 for every hair. Moreover, each problem which is solved opens out 

 vistas, as it were, of others perhaps even more interesting. With this 

 great change the name of our illustrious countryman, Darwin, is inti- 

 mately associated, and the year 1859 will always be memorable in sci- 

 ence as having produced his great work on " The Origin of Species." 

 In the previous year he and Wallace had published short papers, in 

 which they clearly state the theory of natural selection, at which they 

 had simultaneously and independently arrived. We can not wonder 

 that Darwin's views should have at first excited great opposition. 

 Nevertheless, from the first they met with powerful support, especially 

 in this country, from Hooker, Huxley, and Herbert Spencer. The 

 theory is based on four axioms : 



" 1. That no two animals or plants in nature are identical in all 

 respects. 2. That the offspring tend to inherit the peculiarities of 

 their parents. 3. That of those which come into existence, only a 

 small number reach maturity. 4. That those which are, on the whole, 

 best adapted to the circumstances in which they are placed are most 

 likely to leave descendants." 



Darwin commenced his work by discussing the causes and extent 

 of variability in animals, and the origin of domestic varieties ; he 

 showed the impossibility of distinguishing between varieties and spe- 

 cies, and pointed out the wide differences which man has produced in 

 some cases as, for instance, in our domestic pigeons, all unquestion- 

 ably descended from a common stock. He dwelt on the struggle for 

 existence (which has since become a household word), and which, in- 

 evitably resulting in the survival of the fittest, tends gradually to 

 adapt any race of animals to the conditions in which it occurs. While 

 thus, however, showing the great importance of natural selection, he 

 attributed to it no exclusive influence, but fully admitted that other 

 causes the use and disuse of organs, sexual selection, etc. had to be 

 taken into consideration. Passing on to the difficulties of his theory, 

 he accounted for the absence of intermediate varieties between species, 

 to a great extent, by the imperfection of the geological record. But, 

 if the geological record be imperfect, it is still very instructive. The 



