352 EVOLUTION, OLD AND NEW. 



selection is the most important, but not exclusive means 

 of modification, lie means that the survival in the 

 struggle for existence of those creatures which are best 

 fitted to comply with the conditions of their existence 

 is the most important, but not exclusive means whereby 

 the descendants of a creature, we will say, A, have 

 become modified, so as to be now represented by a 

 creature, we will say, B. 



But the word " circonstances" so frequently used by 

 Lamarck for the conditions of an animal's existence, 

 contains, by implication, the idea of animals which shall 

 exist or not according as they fulfil those conditions or fail 

 to fulfil them. Conditions of existence are conditions 

 which something capable of existing must fulfil if it 

 would exist at all, and nothing is a condition of an 

 animal's existence which that animal need not comply 

 with and may yet continue to exist. Again, the words 

 "animals" and "plants" comprehend the ideas of 

 "fit," "fitter," and "fittest," "unfit," "unfitter," and 

 "unfittest" for certain conditions, for we know of no 

 animals or plants in which we do not observe degrees 

 of fitness or unfitness for their "circonstances" or en- 

 vironment, or conditions of existence. 



The use, therefore, of the term " conditions of exist- 

 ence" is sufficient to show that the person using it 

 intends to imply that those animals and plants will live 

 longest (or survive) and thrive best which are best able 

 to fulfil those conditions. Hence it implies neither 

 more nor less than what is implied by the words 

 "struggle for existence, with consequent survival of 

 the fittest" that is to say, if we hold the complying 



