DEVELOPMENT AND CREATION. 3 



we see the organic species, the multiform varieties of 

 animals and plants, vary under our eyes through 

 adaptation, while the similarity of their internal struc- 

 ture is reasonably explicable only by inheritance from 

 common parent - forms, we are forced to assume 

 common parent - forms for at least the great main 

 divisions of the animal and vegetable kingdoms, and 

 for the classes, orders, and so forth. Thus the number 

 of these will be very limited, and the primitive 

 archigonian parent-forms can be nothing else than 

 monads. Whether we finally assume a single common 

 parent-form (the monophyletic hypothesis), or several 

 (the polyphyletic hypothesis), is wholly immaterial to 

 the essence of the theory of descent ; and it is equally 

 immaterial to its fundamental idea what mechanical 

 causes are assumed for the transformation of the 

 varieties. This assumption of a transformation or 

 metamorphosis of species is, however, indispensable, 

 and the theory of descent is very properly called also 

 the " metamorphosis hypothesis," or " doctrine of trans- 

 mutation ; " as well as Lamarckism, after Jean Lamarck, 

 who first founded it in 1 809. 



III. The doctrine of elimination, or the selection 

 theory, as the doctrine especially of " choice of breed 

 or selection," assumes that almost all, or at any rate 

 most, organic species have originated by a process of 

 selection; the artificial varieties under conditions of 



