CENTEES OF CKEATION. 353 



which influence the origin of a new species by natural 

 selection — should have worked together in exactly the 

 same agreement and combination more than once in the 

 earth's history, or should have been active at the same time 

 at several different points of the earth's surface. 



On the other hand, I consider it to be very probable that 

 certain exceedingly imperfect organisms of the simplest 

 structure, forms of species of an exceedingly indifferent 

 nature, as, for example, many single-celled Protista, but 

 especially the Monera, the simplest of them all, should have 

 several times or simultaneously arisen in their specific form 

 in several parts of the earth. For the few and very simple 

 conditions by which their specific form was changed in the 

 struggle for life may surely have often been repeated, in 

 the course of time, independently in difierent parts of 

 the earth. Further, those higher specific forms also, which 

 have not arisen by natural selection, but by hybridism (the 

 previously-mentioned hybrid species, pp. 147 and 275), may 

 have repeatedly arisen anew in different localities. As, 

 however, this proportionately small number of organisms 

 does not especially interest us here, we may, in respect 

 of chorology, leave them alone, and need only take 

 into consideration the distribution of the great majority 

 of animal and vegetable species in regard to which the 

 single origin of every species in a single locality, in its 

 so-called " central point of creation," can be considered as 

 tolerably certain. 



Every animal and vegetable species from the beginning 

 of its existence has possessed the tendency to spread beyond 

 the limited locality of its origin, beyond the boundary of 

 its "centre of creation," or, in other words, beyond its 



