2l6 BIOLOGICAL LECTURES. 



dealing with this question, are of comparatively recent origin, 

 mainly growths of the last fifty years. It would be a little 

 strange if all this work had merely increased our knowledge of 

 details, and left us drifting back to the issues as they stood one 

 or more centuries ago. But that is practically what we are told 

 by some who rise to champion the epigenesis of Harvey and 

 Wolff. That is the "circuitus theoreticus" discovered by 

 Mr. Bourne. The discovery assuredly deserves embalmment by 

 the side of Harvey's solution of the "circuitus gallinaceus" \ 

 " Quodnam eorum fit prius ovum-ne, an gallina ? Quippe hac 

 naturd prior exstitit, illud autem tempore" (Ex. XXVIII). It 

 has been left to an " epigenesist " of our day to revive this old 

 riddle of Plutarch, and try to palm it off as a sample of modern 

 evolution. 



When we find Harvey gravely discussing such questions and 

 offering such verbal somersaults as solutions, are we reminded 

 of progress or of retrogression in standpoints ? And when this 

 "circuitus gallinaceus" is brought forward as an evidence that 

 there must be a "vis enthea" in our common poultry which 

 sustains this perpetual " revolution from fowl to egg and from 

 egg back to fowl," does it suggest modern evolution, or 

 the kindred notions of Wolff and Blumenbach ? When the 

 first step in preparation for development is pictured as a reduc- 

 tion of a portion of the albumen to " a more spirituous and bet- 

 ter digested fluid," under the influence of a " calidum innatum" 

 directed by Divinity; and when the egg is defined as a 

 41 primordium vegetate" which may come from living parents, 

 but which may also arise spontaneously and from putrefaction, 

 by a sort of accidental parentage, are we led back to Aristotle, 

 or forward to present views ? 



As Robert Willis has well said, Harvey wrote his work on 

 generation in " the harness of Aristotle," and with "the bit of 

 Fabricius between his teeth." Nearly everything that is usu- 

 ally appealed to in his work in illustration of the principles of 

 epigenesis may be credited to the Stagirite. Whatever adum- 

 bration of the law of genetic continuity (homogenesis), as now 

 understood, is to be found in the Exercitationes, may be traced 

 to the same source of inspiration. The significance of that 



