THE STATUS OF MAN. 261 



ness of the species concept, and the diversity of opinion among 

 evolutionists is mainly to blame. 



We will later take up the question, whether there is a speci- 

 fic difference between what are commonly called different 

 races. Here the differences are so obvious and so constant, 

 that Zoologists do not hesitate. We will first take up the ques- 

 tion whether there is any possibility of specific diversity 

 within one nation. 



We know that two species can coexist in one environment, 

 under circumstances which admit of frequent intercrossing, 

 and that such species may yet conserve their identity, even if 

 the hybrids produced are perfectly fertile. We know that such 

 tests as the "sterility of hybrids" test for specific diversity are 

 inadequate. If we refused to see distinct species where fertile 

 hybrids are produced, there would be large groups of animals 

 and plants, each comprising many true-breeding forms of great 

 diversity, in which no species could be distinguishable, such as 

 the great diverse group of the cattle, Bos, or the surface-feeding 

 ducks, Anas. 



Two species can coexist in one environment, if only there is 

 a multitude of individuals of each species, and if conditions are 

 so, that the number of intra-specific matings remain far below 

 that of the inter-specific matings. We know, that the tree-rat 

 and house-rat in Java, and probably in North Africa inter-breed 

 wherever they meet. The fact that there are localities where 

 there are houses, habitable from a rats point of view but no 

 good trees, and also localities where there are suitable fruit- 

 trees, oilpalms, dates, coconut-palms, but no houses, keeps 

 these two rats separate. In the villages, where good houses and 

 good trees almost touch, hybrids are constantly being pro- 

 duced, but these are so far in the minority as compared with the 

 house-rat millions and the tree-rat millions that they are swal- 

 lowed up in the multitude. We can calculate how small are 

 the chances of hybrids to affect the variability of a species into 

 which they merge, and we have discussed the fact that a cer- 

 tain number of animals do not have an equally large number of 



