WHAT ARE SPECIES 



several peculiarities of habit and of geographical distribution 

 might have been brought about — whether, if this were done, 

 the "origin of species " would be discovered, the great 

 mystery solved, he would ^mdoubtedly have replied in the 

 affirmative. He would probably have added that he never 

 expected any such marvellous discovery to be made in 

 his lifetime. But so much as this assuredly ^Ii\ Dar^vin has 

 done, not only in the opinion of his disciples and admirers, 

 but by the admissions of those who doubt the completeness 

 of his explanations. For almost all their objections and 

 difficidties apply to those larger differences which separate 

 genera, families, and orders from each other, not to those which 

 separate one species from the species to which it is most nearly 

 allied, and from the remaining species of the same genus. They 

 adduce such difficulties as the first development of the eye, or 

 of the milk-producing glands of the mammalia ; the wonderful 

 instincts of bees and of ants ; the complex arrangements for 

 the fertilisation of orchids, and numerous other points of 

 structure or habit, as not being satisfactorily explained. But 

 it is evident that these peculiarities had their origin at a very 

 remote period of the earth's history, and no theory, however 

 complete, can do more than afford a probable conjecture as to 

 how they were produced. Our ignorance of the state of the 

 earth's siu-face and of the conditions of life at those remote 

 periods is very great ; thousands of animals and plants must 

 have existed of which we have no record ; while we are 

 usually Avithout any information as to the habits and general 

 life-history even of those of which we possess some fragmentary 

 remains ; so that the truest and most complete theory would 

 not enable us to solve all the difficult problems which the 

 whole course of the development of life upon our globe 

 presents to us. 



What we may expect a true theory to do is to enable us 

 to comprehend and follow out in some detail those changes in 

 the form, structure, and relations of animals and plants which 

 are effected in short periods of time, geologically speaking, 

 and which are now going on around us. AVe may expect it 

 to explain satisfactorily most of the lesser and superficial 

 differences which distinguish one species from another. AVe 

 may expect it to throw light on the mutual relations of the 



