Species and Logical Deduction. Ill 



descent ; and the species goes on indefinitely 

 throughout time, extending over the globe. Retro- 

 spectively also the species must have subsisted thus 

 with respect to likeness, to fertility, and uninter- 

 rupted descent, from the time one primitive pair 

 produced this collection which originated in them. 

 Whence did that pair originate ? Darwinism does 

 not say, beyond suggesting that there were four or 

 five original stocks from which all species started. 

 Evolution, in the wider sense, must go far beyond. 

 And though, as we heard before (No. 98), even such 

 ardent evolutionists as Haeckel and Vogt are now 

 reduced to admitting separate origins for the princi- 

 pal species, still genuine evolution must go on boldly 

 to affirm that all organic life sprang from non-life; 

 and, if necessary for the purpose, it must affirm 

 spontaneous generation. But of that after a while 

 (No. 154-160). 



123. In the meantime we must take note of a 

 second corollary, with respect to the essential like- 

 ness, which, as the axiom says, is the 2 Unitieg 

 ruling attribute of a species, simile simili and Varieties 

 gaudet, "Like rejoiceth in like." That in Nature - 

 likeness consists first and foremost in a unity of 

 function, by means of which it is inclusively fertile 

 and exclusively sterile. It sets up specific barriers, 

 within which it includes all individuals and varieties 

 of the one descent, while it excludes all of any other 

 descent. If we look out over the organic world at 

 large, we see these specific barriers maintaining all 



