44 ZOOLOGICAL PHILOSOPHY 



finally, the power resulting from the more or less frequent use of any 

 organ to modify that organ either by strengthening, developing and 

 increasing it, or by weakening, reducing, attenuating it, and even 

 making it disappear. 



With regard to plants, the same thing may be seen as a result of 

 new conditions on their manner of life and the state of their parts ; 

 so that we shall no longer be astonished to see the considerable changes 

 that we have brought about in those that we have long cultivated. 



Thus, among living bodies, nature, as I have already said, definitely 

 contains nothing but individuals which succeed one another by 

 reproduction and spring from one another ; but the species among 

 them have only a relative constancy and are only invariable tem- 

 porarily. 



Nevertheless, to facilitate the study and knowledge of so many 

 different bodies it is useful to give the name of species to any col- 

 lection of like individuals perpetuated by reproduction without change, 

 so long as their environment does not alter enough to cause varia- 

 tions in their habits, character and shape. 



Of the Species Alleged to be Lost. 



I am still doubtful whether the means adopted by nature to ensure 

 the preservation of species or races have been so inadequate that entire 

 races are now extinct or lost. 



Yet the fossil remains that we find buried iii the soil in so many 

 different places show us the remains of a multitude of different animals 

 which have existed, and among which are found only a very small 

 number of which we now know any living analogues exactly alike. 



Does this fact really furnish any grounds for inferring that the species 

 which we find in the fossil state, and of which no living individual 

 completely similar is known to us, no longer exist in nature ? There 

 are many parts of the earth's surface to which we have never pene- 

 trated, many others that men capable of observing have merely 

 passed through, and many others again, like the various parts of the 

 sea-bottom, in which we have few means of discovering the animals 

 living there. The species that we do not know might well remain 

 hidden in these various places. . 



If there really are lost species, it can doubtless only be among the 

 large animals which live on the dry parts of the earth ; where man 

 exercises absolute sway, and has compassed the destruction of all 

 the individuals of some species which he has not wished to preserve 

 or domesticate. Hence arises the possibility that animals of the genera 

 Palaeotherium, Anoplothermm, Megalonix, MegatJierium, Mastodon, 

 of M. Cuvier, and some other species of genera previously known, 



