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 epigcnesis, 

 or successive differentiation of a relatively homo 

 geneous rudiment into the parts and structures 

 which are characteristic of the adult. 



&quot; Et primo, quidem, quoniam per cjngcncsin sive partium 

 superexorientiuin additamentum pullum fabricari cerium est : 

 qvuBiiam pars ante alias onines cxstruatur, et quid de ilia ejusque 

 generandi modo observanduin veniat, dispicieiiius. Ilatum sane 

 est et in ovo manifesto apparet quod Aristotclcs de perfeetorum 

 animalium generatione enuntiat : nimirum, non omnes partes 

 simul fieri, sed ordine aliam post aliam ; primumque existere 

 particulam genitalem, cujus virtute postea (tanquam ex principle 

 quodam) reliquse omnes partes prosiliant. Qualem in plantanim 

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

 tuberantem cernimus, totius futurse arboris principium. Estquc 

 hccc particula vclutfilius emancipatus seorsumque collocatus, et 

 principium per se vivens ; undc postea mcmbrorum ordo dcscrib- 

 itur ; et quaxunquc ad absolvcndum animal pertinent, dispon- 

 untiir. 1 Quoniam enim nulla pars sc ipsam general; sed post- 

 quam gencrata est, sc ipsam jam auget ; ideo cam primum oriri 

 necesse est, qucv principium augcndi contineat (sive enim planta, 

 sive animal est, ceque omnibus incst quod vim habcat vegctandi, 

 sive mitricndi),&quot; simulque reliquas omnes partes suo quamque 

 ordine distinguat et formet ; proindeque in eadem primogenita 

 particula anima primario inest, sensus, motusque, et tatius vitne 

 auctor et principium. &quot; (Exercitatio 51.) 



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



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



