268 EVOLUTION, OLD AND NEW. 



nature of the distinction between species and yarieties 

 is so well exposed, " I shall show," says Lamarck (in 

 substance, but I am compelled to condense much), 

 " that the habits by which we now recognize any species, 

 are due to the conditions of life [circonstcmces] under 

 which it has for a long time existed, and that these 

 habits have had such an influence upon the structure 

 of each individual of the species, as to have at length 

 modified this structure, and adapted it to the habits 

 which have been contracted,* 



" The individuals of any species," he continues, " cer- 

 tainly resemble their parents ; it is a universal law of 

 nature that all offspring should differ but little from 

 its immediate progenitors, but this does not justify the 

 ordinary belief that species never vary. Indeed, natu- 

 ralists themselves are in continual difficulty as regards 

 distinguishing species from varieties; they do not 

 recognize the fact that species are only constant as 

 long as the conditions in which they are placed are 

 constant. Individuals vary and form breeds which 

 blend so insensibly into the neighbouring species, that 

 the distinctions made by naturalists between species and 

 varieties, are for the most part arbitrary, and the con- 

 fusion upon this head is becoming day by day more 

 serious, f 



" Not perceiving that species will not vary as long as 

 the conditions in which they are placed remain essen- 

 tially unchanged, naturalists have supposed that each 

 species was due to a special act of creation on the part 

 of the Supreme Author of all things. Assuredly, nothing 

 » ' Phil. Zool.,' torn. i. p. 72. f Pages 7X-73. 



