LECTURE IV 



LAMARCK 



! Conclusive proof of the inheritance of the effects of the direct 

 action of the conditions of Hfe may be found at any moment, for 

 all one knows to the contrary ; but even if they who are acquainted 

 with no positive evidence think, with the writer, that a dogmatic 

 assertion, from negative evidence, or in the absence of all evidence, 

 that these effects are not inherited, or cannot be inherited, would 

 be rash and unscientific, they may, nevertheless, be interested in 

 an attempt to test the value of the assumption that they are inher- 

 ited ; admitting, in the interest of clear thinking, that the assump- 

 tion is reasonable and admissible. 



That " inheritance of acquired characters " might produce some 

 system of living nature seems probable ; if we start with organisms 

 with such constitution that this "factor" tends to produce modifi- 

 cations which are both adaptive and inherited. That it has not 

 produced, or materially aided in producing, the system which we 

 know seems certain. 



Our business is to study that which is, not that which might 

 be ; and I shall try to show, as it has been shown again and again, 

 that the adjustments which are exhibited by living things are such 

 as to show that the " inheritance of acquired characters " has played 

 no essential part in their production. 



The most extreme Lamarckian must admit that no organism can 

 transmit or inherit modifications produced by the conditions of 

 any life except its own, or that of its ancestors. The nurture 

 of A cannot be transmitted by B ; nor can it be part of the inherited 

 nature of B's descendants unless they are also descended from A. 

 How, then, are we to explain such things as the bee's sting or the 



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