562 THE POPULAR SCIENCE MONTHLY 



common to them all. And these related species have probably been separated 

 from one another only through the influences of climate and food, and by the 

 lapse of time, which brings about all possible combinations and gives play to all 

 the agencies that make for variation, for improvement, for alteration and for 

 degeneration. 81 



Even the groupings which he gives, Buffon adds, can not be re- 

 garded, in the existing state of knowledge, as correctly and exclusively 

 enumerating all the apparent species which are really akin to one 

 another. The number of separate species which he lists, he intimates, 

 is probably much too great. But at all events, he concludes with pride, 

 his work is the first real attempt at an ornithologie historique. 



The purpose of the present inquiry does not call for any extended 

 exposition of Buffon's views about the causes of modification in animals 

 and the ways in which quasi-species are formed. In the essay " De la 

 degeneration des animaux " the subject is discussed at the length of 

 over sixty quarto pages; the theories there advanced have been suffi- 

 ciently accurately summarized by many previous writers. In brief, the 

 factors in modification which he mentions as the most important are 

 changes of climate (in which the most potent influence is temperature), 

 changes of food, and the effects of domestication. But it is evident that 

 he also believed in a general tendency to variation in the germ, and in 

 the influence of acquired habits, of the use and disuse of parts, and of 

 acquired lesions and mutilations. Thus he explains the humps, and the 

 callosities on the knees and chest, of the camel and the llama as due to 

 the habits of those animals under domestication. Similarly, the cal- 

 losities on the haunches of the baboons arise from the fact that " the 

 ordinary position of these animals is a sitting one — so that the hard 

 skin under the haunches has even become inseparable from the bone 

 against which it is continually pressed by the weight of the body." 

 These theories, of course, take for granted the inheritance of acquired 

 characters, which Buffon also (less cautious here than Maupertuis 32 ) 

 explicitly asserts. It is, I suppose, also well known that Buffon called 

 attention (as Linnaeus did independently) to the struggle for existence 

 between species, due to the excessive multiplication of individuals, and 

 pointed out how an equilibrium comes to be established (so long as ex- 

 ternal conditions remain constant) by means of this opposition. 



It may be said that the movement of nature turns upon two immovable 

 pivots — one, the boundless fecundity which she has given to all species; the 

 other, the innumerable difficulties which reduce the results of that fecundity, 

 and leave throughout time nearly the same number of individuals in every 

 species. 83 



Buffon, in fact, rather over-worked this notion of a stable equilib- 

 rium, which rested upon the assumption of an approximate equality 



81 "Hist, des Oiseaux, " I., 1770, preface. 



82 Cf. Lovejoy, "Some Eighteenth Century Evolutionists," Pop. Sci. 

 Monthly, July, 1904, p. 248 n. 



Hist. Nat.," V., 1755, p. 252. 



Bll 



