188 EVOLUTION IN BIOLOGY vi 



new organism by the process of generation takes 

 place, not suddenly, by simultaneous accretion of 

 rudiments of all, or of the most important, of the 

 organs of the adult ; nor by sudden metamorphosis 

 of a formative substance into a miniature of the 

 whole, which subsequently grows ; but by cpigcnesis, 

 or successive differentiation of a relatively homo- 

 geneous rudiment into the parts and structures 

 which are characteristic of the adult. 



" Et primo, quidem, quoniam per epigenesm sive partium 

 superexorientium additamentum pullum fabricari certum est : 

 qusenam pars ante alias onmes exstmatur, et quid de ilia ejusque 

 generandi inodo observandum veniat, dispiciemus. Ratum sane 

 est et in ovo manifesto apparet quod Aristoteles de perfectorum 

 animalium generatione enuntiat : nimirum, non omnes partes 

 simul fieri, sed ordine aliam post aliam ; primumque existere 

 particulam genitalem, cujus virtute postea (tanquam ex principio 

 quodam) reliquae omnes partes prosiliant. Qualem in plantarum 

 seminibus (fabis, puta, aut glandibus) gemmam sive apicem pro- 

 tuberantem cernimus, totius futurae arboris principium. Estque 

 hcec particula velutjilius emancipatus seorsumqiic collocatus, et 

 principium per se vivens ; unde postea membrorum ordo describ- 

 itur ; et, qucecunqiie ad absolvendum animal pertinent, dispon- 

 untur. 1 Quoniam enim nulla pars se ipsam generat; sed post- 

 quatn generata est, se ipsam jam auget ; ideo earn primum oriri 

 necesse est, quce principium augendi contineat (sive enim planta, 

 sive animal est, ceque omnibus inest quod vim habeat vcgetandi, 

 sive nutriendi)," simul que reliquas omnes partes suo quamque 

 ordine distinguat et formet ; proindeque in eadem primogenita 

 particula anima primario inest, sensus, motusque, et totius vitse 

 auctor et principium." (Exercitatio 51.) 



1 De Generatione Animalium, lib. ii. cap. x. 



2 De Generatione, lib. ii. cap. iv. 



