THE 'NATURALIST'S VOYAGE.' 365 



the east and west of the Andes (1st edit. p. 399) : " Unless 

 we suppose the same species to have been created in two dif- 

 ferent countries, we ought not to expect any closer similarity 

 between the organic beings on the opposite sides of the 

 Andes than on shores separated by a broad strait of the sea." 

 In the 2nd edit. p. 327, the passage is almost verbally identi- 

 cal, and is practically the same. 



There are other passages again which are more strongly 

 evolutionary in the 2nd edit., but otherwise are similar to the 

 corresponding passages in the 1st edition. Thus, in describ- 

 ing the blind Tuco-tuco (1st edit. p. 60 ; 2nd edit. p. 52), in 

 the first edition he makes no allusion* to what Lamarck might 

 have thought, nor is the instance used as an example of modi- 

 fication, as in the edition of 1845. 



A striking passage occurs in the 2nd edit. (p. 173) on the 

 relationship between the "extinct edentata and the living 

 sloths, ant-eaters, and armadillos." 



" This wonderful relationship in the same continent be- 

 tween the dead and the living, will, I do not doubt, hereafter 

 throw more light on the appearance of organic beings on our 

 earth, and their disappearance from it, than any other class 

 of facts." 



This sentence does not occur in the 1st edit., but he was 

 evidently profoundly struck by the disappearance of the gigan- 

 tic forerunners of the present animals. The difference be- 

 tween the discussions in the two editions is most instructive. 

 In both, our ignorance of the conditions of life is insisted on, 

 but in the second edition, the discussion is made to lead up 

 to a strong statement of the intensity of the struggle for life. 

 Then follows a comparison between rarity * and extinction, 

 which introduces the idea that the preservation and domi- 

 nance of existing species depend on the degree in which they 

 are adapted to surrounding conditions. In the first edition, 



* In the second edition, p. 146, the destruction of Niata cattle by 

 droughts is given as a good example of our ignorance of the causes of rar- 

 ity or extinction. The passage does not occur in the first edition. 



