THE UNITY OF THE HUMAN SPECIES. 6g 



What I have just said of the turkey might also be said of the rab- 

 bit. The wild-rabbit lives all around us in our downs, in our woods 

 and he does not resemble, or resembles but little, our domestic rab- 

 bit. These, you know, are both great and small, with short hair, and 

 with silky hair ; that they are black and white, yellow and gray, 

 spotted and of uniform color. In a word, this species comprehends a 

 great number of different races, all constituting one and the same spe- 

 cies with the wild stock which still lives around us. 



From these facts, that could be multiplied, we have to draw an im- 

 portant consequence, to which I call your attention : 



A pair of rabbits, left in a plain where they would encounter no 

 enemies, in a few years would fill it with their descendants, and, in a 

 little while, all France would be easily peopled. "We have just seen 

 that a single stalk of coffee gave birth to all the coffee-trees now found 

 in America. 



The wild-turkeys and their domestic offspring, the wild-rabbits and 

 their captive descendants, may then be considered by the naturalist as 

 equally arising from a primitive pair. 



Gentlemen, this is the stamp of a species. Whenever you see a Sfi* 

 greater or less number of individuals, or groups of animals, or vege- 

 tables, if, for one reason or another, you can look upon them as descend- 

 ants of a single primitive pair, you may say you have before you a 

 species y if from group to group there are differences, you say these are 

 the races of that species. 



Observe carefully, gentlemen, that, in thus expressing myself, I 

 have not stated for certain the existence of this primitive pair of the 

 stock of rabbits or of the stock of turkeys. I affirm no such thing, 

 because neither experiment nor observation the two guides we should 

 always follow in science can aid us on this point. I only say to you, 

 every thing is as if they had been derived from a single pair. 



You see, after all, the question of species and of race is not very 

 difficult to comprehend, nor even very difficult to settle when we know 

 the wild type, when we have the historic data which enable us to con- 

 nect with this type the more or less different groups which domestica- 

 tion has detached. But when we do not know the wild type, when the 

 historic data are lost, the question, on the contrary, becomes extremely 

 difficult at the first step, because differences that we encounter from in- 

 dividual to individual, and, above all, from group to group, might be 

 considered as specific differences. 



Happily, Physiology comes now to our relief. We encounter here 

 one of those great and beautiful general laws upon which the estab- 

 lished order depends, and which we admire more the more we study. 

 This is the law of cross-breeding a law which governs animals as 

 well as vegetables, and is, of course, applicable to man himself. 



You know what is meant by the word crossing. We mean by it 

 all marriage occurring between animals that belong either to two 



