142 



SPECIES AND THEIR ORIGIN 



vidual, or from a pair of individuals — in each case precisely 

 resembling, in all essential respects, their existing descend- 

 ants — which came into existence by a process outside the 

 ordinary course of nature and known as Creation. On this 

 hypothesis the history of the genus Zoothamnium would be 

 represented by the diagram (Fig. 28) ; each of the species 

 being derived from a single individual which came into 



Existing individuals 



i.arbvtoula Z.alternant Z.dlohotomum Z.slmphx 



Z.affint 



Ancestral Indiuiduais 



Fig. 28. — Diagram illustrating the origin of the species of 

 Zoothamnium by creation. 



existence, independently of the progenitors of all the other 

 species, at some distant period of the earth's history. 



Notice that on this theory the various species are no more 

 actually related to one another than is either of them to 

 Vorticella, or for the matter of that to Homo. The in- 

 dividuals of any one species are truly related since they all 

 share a common descent, but there is no more relationship 

 between the individuals of any two independently created 

 species than between any two independently manufactured 



