44 THE PHYSICAL BASIS OF LIFE 



and by Boveri, that a non-nucleated fragment of an un- 

 fertilized egg, may be fertilized by a sperm ("merog- 

 ony") and may develop into a perfectly formed dwarf 

 larva closely similar to that derived from an isolated blas- 

 tomere (Fig. 19).-' Even more astonishing was the con- 

 verse discovery by Driesch and zur Strassen that one 

 larva, normally formed but of double the normal size, may 

 arise from two eggs fused to form one ' ' giant ' ' Qgg ( Fig. 

 20).^^ 



To the developing organism, it would seem to be all one 

 whether it builds with one egg, two eggs, or a piece of an 

 egg. How shall we deal with these facts under the mecha- 

 nistic assumption of an original fixed structural pattern 

 in the egg? Or, if we prefer the other horn of the di- 

 lemma, granting that the egg can at will make over the 

 original pattern so as to fit a new emergency, what kind 

 of original configuration in the germ makes possible such 

 an operation and determines its character % 



Difficulties of this type, according to Driesch 's argu- 

 ment, constitute the rock on which the whole mechanistic 

 interpretation of organization and development splits."^ 

 The argument may fail to convince us — it does fail ; but 

 it still remains without adequate answer if it be not unan- 

 swerable. All, on the contrary, now points to the essential 

 correctness of Driesch 's contention that at the real begin- 

 ning of development the cytoplasm of the egg is devoid of 

 any structural pattern or machine-like configuration that 

 foreshadows the plan of the future embryo. Not alone the 

 structural details of the embryo but the very plan on 

 which it is built is constructed anew in the course of de- 

 velopment. May we then seek a solution of the puzzle in 

 the nucleus of the egg, in the hope of finding here the 

 primary determining causes of the organization of the 

 egg considered as a whole ? Perhaj)s. Whether the nucleus 



