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Show 118 CONDITIONS AFI~ECTING THE in nature! Indeed, I do not know that it is possible by direct evidence to prove the origin of a variety in nature, or to prove selective breeding; but I will tell you what we can prove-and this comes to the same thing-that varieties exist in nature within the limits of species, and, what is more, that when a variety has come into existence in nature, there are natural causes and conditions, which are amply competent to play the part o~ a selective breeder; and although that is not quite the evidence that one would like to havethough it is no~ direct testimony-yet it is exceeding good and exceedingly powerful evidence in its way. As to the first point, of varieties existing amono- natural species, I might appeal to the universal expe~ience of every naturalist, and of any person who has ever turned any attention at all to the characteristics of plants and animals in a state of nature; but I may as well take a few definite cases, and I will begin with Man himself. . I am o~e of those who believe that, at present, there IS no evidence whatever for saying, that mankind sprang originally from any more than a sino-le pair. I b ' must say, that I cannot see any good ground whatever, or even any tenable sort of evidence for believing that .there is more than one species of ~an. Nevertheless, as you know, just as there are numbers of varieties in animals, so there are remarkable varieti~ s. of men. I speak not merely of those broad and distinct variations which you see at a glance. Everybody' of course, knows the difference between a Negro and a white man, and can tell a Chinaman from an Englishman. They each have peculiar characteristics of colour and physiognomy; but you must recollect :PERPETUATION OF LIVING BEINGS. 119 that the characters of these races go very far deeper -they extend to the bony structure, and to the characters of that most important of all organs to us-the brain; so that, among men belonging to different races, or even within the same race, one man shall have a brain a third, or half, or even seventy per cent. bigger than another; and if you take the whole range of human brains, you will find a variation in some cases of a hundred per cent. Apart from these variations in the size of the brain, the cha:racters of the skull vary. Thus if I draw the figures of a Mongul and a Negro head on the blackboard, in the case of the last the breadth would be about seven-tenths, and in the other it would ·be nine-tenths' of the total length. So that you see there is abundant evidence of variation among men in their natural condition. And if you turn to other animals there is just the same thing. The fox, for example, which has a very large geographical distribution all over Europe, and parts of Asia, and on the American Continent, varies greatly. There are mostly large foxes in the North, and smaller ones in the South. In Germany alone, the foresters reckon some eight different sorts. Of the tiger, no one supposes that there is more than one species; they extend from the hottest parts of Bengal, into the dry, cold, bitter steppes of Siberia, into a latitude of 50°,-so that t~ey may even prey upon the reindeer. These tigers have exceedingly different characteristics, but still they all keep their general features, so that there is no doubt as to their being tigers. The Siberian tiger bas a thick fur, a small mane, and a longitudinal stripe down the back, |