1 8 59-] LYELL'S CRITICISMS. 213 



middle point of their respective ranges, and which, as we 

 positively know, can perfectly well withstand a little more 

 heat and cold, a little more damp and dry, but which in 

 the metropolis of their range do not exist in vast numbers, 

 although, if many of the other inhabitants were destroyed 

 [they] would cover the ground. We thus clearly see that 

 their numbers are kept down, in almost every case, not by 

 climate, but*- by the struggle with other organisms. All this 

 you will perhaps think very obvious ; but, until I repeated it 

 to myself thousands of times, I took, as I believe, a wholly 

 wrong view of the whole economy of nature. . . . 



Hybridism. I am so much pleased that you approve of 

 this chapter ; you would be astonished at the labour this 

 cost me ; so often was I, on what I believe was, the wrong 

 scent. 



Rudimentary Organs. On the theory of Natural Selection 

 there is a wide distinction between Rudimentary Organs and 

 what you call germs of organs, and what I call in my bigger 

 book " nascent " organs. An organ should not be called rudi- 

 mentary unless it be useless as teeth which never cut through 

 the gums the papillae, representing the pistil in male flowers, 

 wing cf Apteryx, or better, the little wings under soldered 

 elytra. These organs are now plainly useless, and a fortiori, 

 they would be useless in a less developed state. Natural Selec- 

 tion acts exclusively by preserving successive slight, useful 

 modifications. Hence Natural Selection cannot possibly make 

 a useless or rudimentary organ. Such organs are solely due 

 to inheritance (as explained in my discussion), and plainly 

 bespeak an ancestor having the organ in a useful condition 

 They may be, and often have been, worked in for other pur- 

 poses, and then they are only rudimentary for the original 

 function, which is sometimes plainly apparent. A nascent 

 organ, though little developed, as it has to be developed must 

 be useful in every stage of development. As we cannot 

 prophesy, we cannot tell what organs are now nascent ; and 



