106 Prof. Pictet on the Succession of Organised Beings 



stances which have formed them cease to act, and the old conditions 

 under which they lived have returned, they recover more or less their 

 first form. 3cZ, Races proceeding from a common stock, differ from 

 each other only in characters of little importance and altogether su- 

 perficial ; that is to say, the exterior causes which determine races 

 are incapable of altering the anatomical and essential characters. 



All these facts are the result of numerous observations, and may 

 be considered as demonstrated. They have too often been erro- 

 neously confounded with the less certain deductions we have made, 

 and the direct results which may be drawn from them have been 

 erroneously placed on the same footing as the hypothesis deemed ne- 

 cessary to complete the idea we seek to form of a species. It is 

 principally with the view of drawing attention to the point where 

 the solid basis of facts has been left for the shifting ground of hypo- 

 thesis, that I have dwelt so long on this preliminary analysis. 



The three principal characters of races being established, it has 

 been admitted that beings not presenting them did not proceed from 

 the same stock, and, deducing from this idea the definition of a spe- 

 cies, such as spring from a common origin, and also differ from each 

 other by more important characters than those which separate races, 

 have been considered as beings of the same species. It is impos- 

 sible not to perceive that, in this assertion, the direct results of the 

 observation of facts has been extended by an hypothesis. It is, in 

 reality, unquestionable that animals emanating from the same stock 

 may form races, and even that beings not differing from each other 

 but by their characters of race, have a common origin ; but it is not 

 on that account directly demonstrated that the descendants of a com- 

 mon stock may not differ by more important characters than those 

 which actual science has established in the races now known ; for we 

 know only a small number of species modified in this manner, and 

 in circumstances which, perhaps, are neither the only ones nor the 

 most active. It is not, consequently, directly demonstrated that the 

 beings which differ from each other by more important characters 

 than those of the races with which we are acquainted, have neces- 

 sarily a different origin. I may add, that for my own part I am 

 much disposed to admit the strength of the arguments in favour of 

 this hypothesis ; but I think it necessary, for the distinctness of the 

 discussion, to distinguish it from the facts formerly cited, which pos- 

 sess a degree of certainty that can scarcely be disputed. 



Let us illustrate this by some examples drawn from the applica- 

 tion of the three characters indicated above. It is proved, by ex- 

 tending the first character, that when two beings cannot, by their 

 copulation, give birth to a descendant, or when this descendant itself 

 is incapable of reproduction, they have not had a common origin. 

 This assertion, considered as an axiom by many naturalists, is, how- 

 ever, merely a hypothesis which I think very likely to be true, but 

 not indisputable. Thus the Arab horse and the Flemish horse may 



