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animated nature some races can boast of an immemorial 

 antiquity, whilst others are comparative parve?mes. We have 

 also the clearest evidence that the animals and plants which now 

 inhabit the globe have been preceded, over and over again, by 

 other different assemblages of animals and plants, which have 

 flourished in successive periods of the earth's history, have reached 

 their culmination, and then have given way to a fresh series of 

 living beings. We have, finally, the clearest evidence that these 

 successive groups of animals and plants (faunas and florae) are, to 

 a greater or less extent, directly connected with one another. 

 Each group is, to a greater or less extent, the lineal descendant 

 of the group which immediately preceded it in point of time, and 

 is more or less fully concerned with giving origin to the group 

 which immediately follows it. That this law of " evolution " has 

 prevailed to a great extent is quite certain, but it does not meet 

 all the exigencies of the case, and it is probable that its action 

 has been supplemented by some still unknown law of a different 

 character. It is the obvious working of what Professor Nicholson 

 refers to as " some unknown law," which, I take it, conduces to 

 the indestructibility, or permanency, of type, which for a long 

 time made me doubt the truth of the theory of " evolution." 



Further inquiry and observation have convinced me that 

 natural selection is a true cause, and that whatever may be the 

 final result of our inquiries — whether animated nature be derived 

 from one or many ancestral sources — still the origin of species by 

 natural selection will, I believe, be found to be a true cause. 

 How far the present condition of living beings is due to that 

 cause, and how far, on the other hand, the law of natural selection 

 has been acted on and controlled by other natural laws, such as 

 permanency of type, atavism, etc., how many types of life 

 originally came into being, and whether they arose simultaneously 

 or successively — these and many other questions seem to me to 

 be still unsolved. The field of labour for the biologist is a vast 

 one, and though that great naturalist, Chas. Darwin, has left us the 

 key to the entrance gate, if I may be allowed the simile, there are 

 still many doors closed to us. It seems to me that nothing is 

 more unfair or uncharitable when discussing what, after all, is a 

 question of the modus operandi, than to charge some of those 



