Page:The Harveian oration (electronic resource) - Royal College of Physicians, 1881 (IA b20411911).pdf/30

 tion of the origin of varieties, It was contended by some that human beings so utterly unlike each other as some of these races are must have sprung from distinct progenitors, who had come upon the earth's surface at different times and at distant localities. Such a suggestion was very naturally met by others with the assertion that all belong to the same species.

Here let me just observe that, in the employment of the term species, I mean merely to convey the idea that, however closely any animals are related to each other, they do not belong to the same species if it be ascertained regarding them that the union of the sexes does not produce a prolific offspring. It is quite immaterial to my purpose to inquire further into this proposition, or why it is that the hybrid product of the union, when any such takes place, is incapable of producing progeny; it is only necessary here to define the sense in which the term is employed. I may further add that, whether this word continue to be used by scientific writers, or any other term be substituted for it, the law of Nature remains, and must be recognised. This has, no doubt, deprived much of the contention of its interest, so far as man at least is concerned, because nowhere is there any barrier to the propagation of the species. It has, indeed, been asserted that the mixed breed of certain races has degenerated and died out. Were