XL] EVOLUTION IN BIOLOGY. 275 



relatively homogeneous rudiment into the parts and 

 structures which are characteristic of the adult. 



"Et primd, quidem, quoniam per epigenesin sive partium 

 superexorientium additamentum pullum fabricari certum est : 

 qusenam pars ante alias omnes exstruatur, et quid de ilia ejusque 

 generandi modo 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) reliquse omnes partes prosiliant. Qualem in plantarum 

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

 tuberantem cernimus, totius futurse arboris principium. Estque 

 hcec particula velut filius emancipatus seorsumque collocatus, et prin- 

 cipium per se vivens; unde postea membrorum ordo describitur ; et 

 qucecunque ad dbsolvendum animal pertinent, disponuntur. 1 Quoniam 

 enim nulla pars se ipsam general; sed postquam generata est, se ipsam 

 jam auget ; ideo earn primum oriri necesse est, quce principium augendi 

 contineat (sive enim planla, sive animal est, ceque omnibus inest quod 

 vim habeat vegetandi, sive nutriendi), 2 simulque reh'quas omnes 

 partes suo quamque ordine distinguat et formet ; proindeque in 

 eadem primogenita particula anima primario inest, sensus, mo- 

 tusque, et totius vitae auctor et principium," (Exercitatio 51.) 



Harvey proceeds to contrast this view with that of 

 the " Medici," or followers of Hippocrates and Galen, 

 who, " badly philosophising," imagined that the brain, 

 the heart, and the liver were simultaneously first 

 generated in the form of vesicles ; and, at the same 

 time, while expressing his agreement with Aristotle in 

 the principle of epigenesis, he maintains that it is the 

 blood which is the primal generative part, and not, as 

 Aristotle thought, the heart. 



In the latter part of the seventeenth century, the 



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

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



