EVOLUTION AND EPIGENESIS. 



217 



beautiful aphorism so often ascribed to Harvey, omne vivum 

 ex ovo, hangs on the definition of its last word. As defined 

 by Harvey the whole idea shrinks to the doctrine of Aristotle. 

 It falls far behind Redi's formula, omne vivum ex vivo, which 

 still did not exclude xenogenesis and syngenesis. In order to 

 put modern notions into the expression, we have to read the 

 old "primordium" out, and read in its place everything im- 

 plied in the latest revisions of the germ theory. 



Banish the tradition of spontaneous generation, the meta- 

 physical relics of " vital spirits," "ingenerate heat," "final 

 causes," "generative contagion," "immaterial form," such ex- 

 travagant analogies as that of "uterine conception to mental 

 conception," such concoctions as "antegenial moisture," and 

 other "fabulae" confessed and unconfessed, banish the 

 whole phantasmagoria, and then read "ovum" in all the light 

 of Redi's formula, the cell doctrine, Virchow's formula, 

 Gegenbaur's researches on the egg, and all the corollaries 

 supplied by recent cytological work, and Harvey's dictum 

 comes forth transfigured into truth empyreal, no longer a 

 vague generalization, exceeding in no way what Aristotle 

 had already maintained. 1 



Harvey grasped some details of development that had 

 escaped both Aristotle and Fabricius; but his philosophy of 



1 Harvey concludes the sixty-third exercise with the following from Aristotle: 

 "All living creatures^ whether they swim, or walk, or fly, and whether they come 

 into the world with the form of an animal or of an egg, are engendered in the same 

 way." 



Harvey identifies the " seed," the " egg," the " conception," and the spontane- 

 ous "primordium," on the ground that they all agree in containing the "matter 

 out of which and the efficient cause by which whatsoever is produced is made." 

 " Let us, therefore, say that that which is called primordium among things arising 

 spontaneously, and seed among plants, is an egg among oviparous animals ; i.e., a 

 certain corporeal substance, from which, through the motions and efficacy of an inter- 

 nal principle, a plant or an animal of one description or another is produced ; 

 but the prime conception in viviparous animals is of the same precise nature, a 

 fact which we have found approved both by sense and reason" (Ex. LXIII). 



Aristotle did not insist that his " spontaneous foam-vesicle " must be called an 

 egg ; but he did insist that it was fundamentally the same, inasmuch as it repre- 

 sented both the "matter" and the "efficient." Harvey's assertion that "all ani- 

 mals are in some sort produced from eggs," is a fair summary only of what Aristo- 

 tle affirmed of the "conception," the "egg," and the "worm" (Dt 6V;/. Anim,, 

 lib. Ill, cap. IX). 



