310 On Species. 



Again, in t"he animal kingdom, there is tlie same aversion in 

 nature to intermixture, and it is emotional as well as physical. 

 The supposed cases of fertile hybridity are fewer than among 

 plants. 



Moreover, in both kingdoms, if hybridity be begun, nature 

 commences at once to purify herself as of an ulcer on the sys- 

 tem. It is treated like a disease, and the energies of the species 

 combine to throw it off. The short run of hybridity between 

 the horse and the ass, species very closely related, reaching its 

 end in one single generation^ instead of favoring the idea that per- 

 petuated fertile hybridity is possible, is a speaking protest against 

 a principle that would ruin the system if allowed free scope* 



The finiteness of nature in all her proportions, and the neces- 

 sity of finiteness and fixedness for the very existence of a king- 

 dom of life, or of human science its impress on finite mind, are 

 hence strong arguments for the belief that hybridity cannot se- 

 riously trifle with the true units of nature, and at the best, can 

 only make temporary variations. 



It is fair to make the supposition that in case of a very close 

 proximity of species, there might be a degree of fertile hybridity 

 allowed; and that a closer and closer affinity might give a longer 

 and longer range of fertility. But tlie case just now alluded to 

 seems to cut the hypothesis short; and moreover it is not reason- 

 able to attribute such indefiniteness to nature's outlines, for it is 

 at variance with the spirit of her system. 



Were such a case demonstrated by well- established fiicts, it 

 would necessarily be admitted ; and I would add, that investiga- 

 tions directed to this point are the most important that modern 



science can undertake. 



guraents 



than those drawn from domesticated animals, we may plead the 

 general principle against the possibiliiies on the other side. ^ H 

 there is a law to be discovered, it is a wide and comprehensive 

 law, for such are all iiature's principles. Nature will teach it 

 not in one corner of her system only, but more or less in every 

 part. We have therefore a ri^ht to ask for well-defined facts, 

 taken from the study of successive generations of the interbreed- 

 ing of species known to be distinct. , ., 

 Least of all should we expect that a law, which is so ng^^ 

 among plants and the lower animals, should have its main ex- 

 ceptions in the highest class of the animal kingdom, and its most 

 extravagant violations in the genus Homo ; for if there are more 

 than one species of Man, they have become in the main indeh- 

 nite by intermixture. The very crown of the kingdom has been 

 despoiled ; for a kingdom in nature is perfect only as it retams 

 all its original parts in their full symmetry, undefaced and un- 

 blurred. Man, by receiving a plastic body, in accordance with 



a law that species most capable of domestication should necessa- 



I 



