164 THE DOCTRINE OF DESCENT. 



duction of protoplasm, that primordial organism, from 

 the atoms of its constituents. 



Hence the beginning of life at some bygone period is 

 likewise not susceptible of demonstration; but the com- 

 mencement of animate being at some definite era of de- 

 velopment is a logical necessity, and by no means a vul- 

 nerable point in the doctrine of Descent.^* 



We have already incidentally mentioned a man who, 

 although not so eminent as Darwin, has the glory of 

 having independently discovered the law of natural se- 

 lection, and of having, after Darwin had come forward 

 with his fundamental work, supported the theory of se- 

 lection by a profusion of original observations. This is 

 Alfred Russell Wallace.^^ In a paper, published in 1855, 

 he demonstrated the dependence of ♦^he flora and fauna 

 on the geographical position and geological nature of 

 the district of propagation, and the close connection of 

 the species, according to time and habitat, with kindred 

 species previously existing; and in a second work, in 

 the year 1858, on the inclination of varieties to deviate 

 without limit from the original type, we find a disquisi- 

 tion on the importance of the struggle for existence, the 

 consequences of adaptation, the selection of the most 

 useful, and the replacement of the earlier species by the 

 establishment of the more valuable varieties. We shall 

 repeatedly have occasion to draw upon the rich sup- 

 plies of his researches. 



