232 WHAT IS LIFE 



living matter) consist of two systems, a Y-system 

 and a Z-system, as described. And it is the constitu- 

 tion, the organization, the pattern, of the Z-system 

 of the germ-cell — not the chemical constitution of 

 the matter (the Y-system) of the germ-cell, nor 

 anything else connected with the germ-cell — which 

 primarily determines that given the egg of a Pla- 

 norbis, only a Planorbis can result. 



The egg of any organism never by any possible 

 chance develops into anything but an individual of 

 the same kind as its parent. This phenomenon of 

 specificity cannot be accounted for except on the 

 view which here is briefly stated; on the other hand, 

 specificity, such as is actually observed, inevitably 

 must characterize the process and product due to a 

 germ-cell that is constituted as the theory describes 

 it. 



Suitable conditions predicated, it is the pattern of 

 the grouping of the elementary units that constitute 

 the Z-system of a germ-cell that determines what 

 series of reactions can take place; one series leading to 

 another, and that to the next; and so on, until the 

 limit of reactions proper to the organism (always a 

 dual system), as determined by the germ-cell, has 

 been reached. Obviously, the determinants of the 

 series for any one of the higher organisms lie packed 

 in the microscopic germ-cell. This fact finds its 



