EVOLUTION AND EPIGENESIS. 219 



requisite, molding them in the new being, with consummate 

 art, into the form and likeness of its parents " (Ex. LVII). 



Harvey does not evade the question for which epigenesis 

 itself is responsible ; namely, how is development set in motion 

 and directed ? " Qiiomodo omnia ex wiivoco fiant ? quo pacto 

 scil. idem semper ide^n pjvgeneret?" {De Conceptione, p. 298.) 

 That was to him, as it still is to us, the grand question. It 

 was here that epigenesis found its iiltima Thule, beyond which 

 all was "nonentity," "contagion by non-contingents," ''species 

 sine materia,'' 'Uujtis gratia," etc. The theory vanished in a 

 void. There was no getting over it, and no escape from it. 

 Like begets like, and yet there is a vacuum between them and 

 absolutely nothing to fill it except immaterial '' exejnplaria." 

 " Seeing nothing left," says Harvey, " I have devised this fable 

 (p. 297) . . . preferring a fanciful opinion to none at all " 

 (p. 298). 



No shadow of reproach falls on the immortal discoverer of 

 the circulation of the blood for inventing such a fable and 

 winding up with syllogisms in its support. Two and a half 

 centuries ago, that was the best that could be expected even 

 from a genius that is now deservedly esteemed as a sort of 

 divinity in Embryology as well as in Physiology. But it is a 

 matter of some interest to us that the old epigenesis found its 

 logical end invariably in some fatal fabula, the purpose of which 

 was — in its last analysis — to cover a void of its own creation. 

 A train of orderly appearances is to be accounted for. The 

 nearer we get to the original germ, the more obscure become 

 the phenomena. Heterogeneity sinks gradually out of sight, 

 and the inference is that it terminates in homogeneity. But 

 how is homogeneity "cooked" into heterogeneity.? Epi- 

 genesis is cornered. Seeing how difficult it is to epigenesize 

 something out of nothing, it invokes spiritual agencies and 

 vital forces and assigns them the task. There arise the mys- 

 tical host, — "vegetative soul," "psychic heat," " ingenerate 

 heat," '' vis plastica,'' "vis enthea," "vis essentialis," " nisus 

 formativus," and all the other "nonentities " devised before and 

 since Harvey's day. Aristotle, Harvey, Wolff, and Blumen- 

 bach, all traversed the same problem and landed in the same 



