LECTURE XV. 441 



3. The raceless masses produced by transportation into a 

 foreign climate may, by pure imbreeding^ give rise to a new 

 human race or species, the characters of which might, indeed, 

 become fixed after a few generations, but would require a very 

 long period of time before they can acquire that constancy 

 which distinguishes the original species of mankind. 



4. The various species of mankind present in crossing dif- 

 ferent degrees of fertility. Most of them are between each other 

 indefinitely prolific, as also are their descendants ; in some the 

 fertility is so limited, that no mongrel race can be produced by 

 them. 



5. The mongrel races gradually attain by inbreeding that 

 constancy of chai-acters which distinguishes the original race, 

 so that from this commixture new species may arise. 



6. Heterogeneous races have by intermixture g-iven rise to 

 raceless masses — peoples which present no fixed characters, 

 and form, so to speak, dispersive circles around the original 

 species, which at their points of contact become confluent. 



I cannot deny that these views are not exclusively derived 

 from what is observed in man, but chiefly from what is seen 

 in domestic and wild animals. But this, if I am not mistaken, 

 gives greater weight to them. We are not so blind as to 

 maintain, that the original species of mankind can undergo no 

 change by the influence of surrounding media. We neither 

 deny intermixture nor the mongrel races to which it has given 

 rise, but we are unable to perceive that their existence can 

 entirely obhterate the original difference, or afford a proof for 

 an original unity, which is opposed to all known facts. Again 

 we neither deny the disappearance and extinction of well cha- 

 racterised races, nor the rise of new races and species from the 

 commixtui'e of existing species, intensified perhaps by the influ- 

 ence of external media. All this is confirmed by the facts ob- 

 served in the rest of the animal world. For the development of 

 this view we certainly as little require supernatural influences, or 

 direct interference of foreign forces, as Laplace required a 

 divine interference for celestial mechanics, an hypothesis which 

 a modern pious defender of the unity of species, in the face of 

 all facts, advances in this manner : 



