00 LIFE OF 



most interesting, because these castes could only be 

 developed if the variations which produced them were 

 profitable to the community; "for no amount of exercise, 

 or habit, or volition, in the utterly sterile members of a 

 community could possibly have affected the structure or 

 instincts of the fertile members, which alone leave descen- 

 dants." This fact Darwin considers to be demonstrative 

 against Lamarck's doctrine. At the same time, he admits 

 that instincts are not always perfect, and are liable to 

 make mistakes ; and that no instinct has been produced 

 for the exclusive good of other animals, but that each 

 animal takes advantage of the instincts of others. It is 

 to him " far more satisfactory to look at such instincts as 

 the young cuckoo ejecting its foster-brothers, ants making 

 slaves, the larvae of ichneumonidse feeding within the live 

 bodies of caterpillars, not as specially endowed or created 

 instincts, but as small consequences of one general law, 

 leading to the advancement of all organic beings, namely, 

 multiply, vary, let the strongest live and the weakest 

 die." And here Darwin strikes one of his truest and 

 most helpful notes. It is far more satisfactory to con- 

 template the rapine and war of nature as incidents which 

 aid in working out a grand progress than as multitudinous 

 cruelties, working no good, and in past ages of unknown 

 length merely preluding the struggle and rapine through 

 which man works out his rise or fall. If we agonise that 

 we and our descendants may rise, life is worth living. 



We cannot follow in detail the profoundly suggestive 

 chapters on Hybridism, on the Imperfection of the 

 Geological Record, on the Geological Succession of 

 Organic Beings, on the Geographical Distribution, and 



