Evolution and Epigenesis 105 



We note that theoretically a mixed or intermediate 

 hypothesis would be conceivable, according to which a 

 given part of the organism would be differentiated 

 through the cooperation of causes lying within and with- 

 out it. In case however the causes lying at any moment of 

 ontogeny within the part concerned, do not arise through 

 any antecedent process of epigenetic nature, the develop- 

 ment at least up to this time must be considered as essen- 

 tially purely evolutionary. But if, on the contrary, the 

 internal causes do arise through an antecedent process of 

 epigenetic nature the whole development would then be 

 essentially of that nature. 



Whitman states that the conception of modern evo- 

 lutionists differs essentially from that of the earlier ovists 

 and spermatists ; for they excluded the formation of new 

 structural parts during development, a thing which is nat- 

 urally admitted by the evolutionists of to-day. Accord- 

 ing to Mivart's definition which Whitman accepts com- 

 pletely, "the term evolution may be employed, as it has 

 been, to denote that the successive formation of parts pre- 

 viously not existent is due not to their imposition from 

 without but to their generation from within." 70 



According to this definition which is essentially iden- 

 tical with that of Roux above cited, evolution, it may 

 here be repeated, limits to a minimum the influence which 

 the various other parts of the organism exert upon the 

 development of each part, or considers it as absolutely 

 non-existent, since each part contains within itself, or in 

 any event in its immediate neighborhood, the causes of its 

 progressive development. According to the epigenetic 



70 Whitman: Evolution and Epigenesis. Biol. Lect. at the Mar. 

 Biol. Lab. of Woods Holl, Summer Session 1894. Boston, U. S. A., 

 Ginu, 1896. P. 224. 



