No. 514] 



.I/,'/-; SPECIES EEALITIESi 



vm 



"adult individual" leaves us. The common assumption 

 that there is a fixed, or at least a typical adult state is 

 often more assumption than fact, or if partially true, due 

 to the accident of constant average environmental con 

 ditions. Thus the writer was astonished to find that an 

 adult salamander, tallying with every character of the 

 "typical individual" would yet, under favorable environ- 

 ment, betake itself to a new period of development and. 

 larva like, issue therefrom so changed in its supposedly 

 fixed characters of adulthood that nothing short of con- 

 tinuous observation could convince one of its individual 

 identity, or rather continuity with the former phases of 

 itself. To know individuals, then, means to know life- 

 histories. To know life-histories means to save and sift 

 our perceptual experience, and to solidify it, little by 

 little, into concepts quite as complex as are those in and 

 through which we know species themselves. 



Yet it is admitted that huliriduals arc real, despite this 

 fact that they are made up of phase on phase of shifting 

 though correlated characters, only a part of which we can 

 ever perceive. Why then not" admit that species are real ! 

 Are they not, likewise, groups of interrelated units (units 

 in the practical working sense of this word)! Are not 

 these units-the individuals -bound together by a com- 

 mon genesis as truly as are the cells of the individual's 

 body? Are not these individuals further united by com- 



