The Elements of the Species. 57 



accurately tracing the formation of a given species is 

 certainly a most attractive one ; but its solution falls 

 within the province of comparative biology. 



The origin of specific characters is a matter for 

 physiological investigation, and is of the very highest 

 importance. AVe hardly know what specific characters 

 are. We know, it is true, that elementary species and 

 form.s closely allied to them, are distinguished from one 

 another not by a single feature but by all their organs 

 and peculiarities.^ The difi^erences between two closely 

 allied forms often demand a long and extensive diagnosis. 

 Nevertheless this diagnosis must be regarded as the ex- 

 pression of a single character, a single unit, which arose 

 as such and as such can be lost; the individual factors 

 of which cannot be manifested separately. Theoretically 

 such a group of characters must be regarded as a unit, 

 as a single character.^ It forms a single side of Galton's 

 polyhedron (p. 53). Darwin called such characters 

 the elements of the species and consequently we may 

 call each of the forms distinguished by such an element, 

 an elementary species. 



How these elements of the species arise must sooner 

 or later become the subject of experimental investigation. 

 If we once succeed in solving this question we shall ob- 

 tain not only a much surer foundation for the theory of 

 descent but the prospect of the utilization of this discov- 

 ery for the benefit of mankind. The only means by 

 which the breeder can get new forms is by hybridization, 

 and all that he can do by selection is to intensify the 

 produce and yield of characters already present ; but 



^ This fact forms a hitherto little noticed support for the theory 

 of homotypic cell-divisions as advanced by Hertwig and others and 

 by myself in my Iniracellulare Pangenesis (See e.g. p. 115). 



^ Tniracellulare Pangenesis, p. i6. 



