278 EVOLUTION, OLD AND NEW. 



crooked has been made straight, and the rough places 

 plain ; not even is climate itself stable. Hence changed 

 conditions ; and these involve changed needs and habits 

 of life ; if such changes can give rise to modifications 

 or developments, it is clear that every living body must 

 vary, especially in its outward character, though the 

 variation can only be perceptible after several gene- 

 rations. 



" It is not surprising then that so few living species 

 should be represented in the geologic record. It is 

 surprising rather that we should find any living species 

 represented at all.* 



" Catastrophes have indeed been supposed, and they 

 are an easy way of getting out of the difficulty ; but 

 unfortunately, they are not supported by evidence. 

 Local catastrophes have undoubtedly occurred, as 

 earthquakes and volcanic eruptions, of which the 

 effects can be sufficiently seen ; but why suppose any 

 universal catastrophe, when the ordinary progress of 

 nature suffices to account for the phenomena ? Nature 

 is never "brusque. She proceeds slowly step by step, 

 and this with occasional local catastrophes will remove 

 all our difficulties." t 



In his fourth chapter Lamarck points out that 

 animals move themselves, or parts of themselves, not 

 through impulsion or movement communicated to them 

 as from one billiard ball to another, but by reason of a 

 cause which excites their irritability, which cause is 

 within some animals and forms part of them, while it 

 is wholly outside of others.f 



* ' Phil. Zool.,' torn. i. p. 94. f Pages 95-96. J Page 97. 



