244 



DARWIN. 



in the Journal of the Linncsan Society, June 30, 1858, 

 the first consisting of an abstract of Darwin's manu- 

 scripts of 1S39 and 1844, from the second part, 

 entitled "On the Variation of Organic Beines in a 

 State of Nature; on the Natural Means of Selec- 

 tion ; on the Comparison of Domestic Races and 

 True Species"; also the letter of 1857 to Asa 

 Gray. The second consisted of the paper by Wal- 

 lace, written in February, 1858, entitled "On the 

 Tendency of Varieties to depart indefinitely from 

 the Original Type." 



The line of thought in these two papers is almost 

 directly parallel, as shown in these columns: — 



Darwin. 



There is in Nature a struggle 

 for existence, as shown by Mal- 

 thus and De Candolle. 



Rapid multiplication, if un- 

 checked, even of slow-breeding 

 animals like the elephant . . . 



Great changes in the environ- 

 ment occur. 



It has been shown in a former 

 part of this work that such changes 

 of external conditions would, from 

 their acting upon the reproductive 

 system, probably cause the or- 

 ganization ... to become plastic. 



Can it be doubted that . . . 

 any minute variation in struct- 

 ure, habits, or instincts, adapting 

 that individual better to the new 

 conditions, would tell upon its 

 vigour and health ? 



T Wall.^ce. 



The life of wild animals is a 

 struggle for existence . . . in which 

 the weakest and least perfect must 

 always succumb. 



Even the least prolific of ani- 

 mals would increase rapidly if 

 unchecked. 



A change in the environment 

 may occur. 



(No cause of variation as- 

 signed.) 



Varieties do frequently occur 

 spontaneously. 



All variations from the typical 

 form have some definite effect, 

 however slight, on the habits or 

 capacities of the individuals. 

 Abundance or rarity of a species 

 is dependent on its more or less 



