ORIGIN OF THE INDIVIDUAL 253 



new generation. In this first crude form the PREFORMATION 

 theory demanded the 'encasement' of all future generations 

 one within another in the germ of existing organisms, so that 

 when it was computed that the progenitor of the human race 

 must have contained some two hundred million homunculi 

 (a conservative estimate, to say the least) the reductio ad 

 absurdum was irresistible. 



But careful studies on the transformation of the Hen's egg 

 into the chick soon made it clear that the chick is not pre- 

 formed in the egg. The embryo arises by a gradual process 

 of progressive differentiation from an apparently simple 

 fundament it is a true process of development or EPI- 

 GENESIS. So the upholders of epigenesis versus preforma- 

 tion were before long beyond their depth and in danger of 

 attempting to get something out of nothing lost in the 

 miraculous! 



A statement in such succinct form tends to accentuate the 

 crudities of these two conflicting views " pref ormation ex- 

 plaining development by denying it and epigenesis explaining 

 development by reaffirming it" and it may be well to re- 

 mark that the early embryologists with the means at their 

 command faced a stupendous task of which only recent work 

 has brought a full appreciation. 



The path to progress cleared by the realization that adult 

 structures are not preformed as such in the egg, and that 

 development is not an expansion but the formation the 

 'becoming' by an orderly sequence of events of structures 

 of great complexity out of apparent simplicity, the problem 

 of the embryologist was to determine what the egg structure 

 is and how related to that of the adult. To trace the develop- 

 ment of these studies would involve the history of embryology 

 since the formulation of the cell theory. We must confine 

 ourselves to the bare statement of the new guise in which the 



