216 THE LAW OF JOHANNSEN. 



reacted upon its environment, and as daughter-cells are but 

 halves of it, their characters are those of the mother-cell. Not 

 entirely, because the influences to which daughter-cells are sub- 

 mitted from the moment of division up to the moment at 

 which they are themselves ready for division, may be different 

 from those under which the mother-cell completed growth. 



In the development of metazon, each individual has not 

 been one half of its parent up to the moment at which it had 

 half its bulk. In the ressemblance between parent and off-spring 

 we have here to reckon far more with the genotype, with the 

 set of genes present. 



In so far as the set of genes of the daughter and that of her 

 mother are alike, the reaction upon the environment will be 

 alike, and in so far will they in the long run show likeness: in so 

 far as their genotype is unlike, they will in the long run show 

 difference, provided the difference is one, which affects a gene 

 which has in this type an effect upon development. 



Peculiar conditions, which pertain for a period of a few cell- 

 generations have no appreciable influence upon the final quali- 

 ties. The final qualities of the mother are the result of her devel- 

 opment from one cell to a complex organism under the influen- 

 ce of her genotype which remains the same, and of her environ- 

 ment which may fluctuate. The final characters of the daugh- 

 ter are also caused by her genotype which remains the same 

 and the environment which may fluctuate. The longer the 

 period of development relatively, the more these transient 

 fluctuations in conditions are equalized in the long run, the 

 more therefore likeness becomes a true test for sameness 

 of genotype. 



We may compare the qualities of an adult brown bear, 

 which has grown up through several dry and wet seasons, 

 through fat and lean days, passed through several hibernations 

 to the qualities of an adult dauhgter of her age and experience, 

 and observe a certain likeness as compared to a certain unlike- 

 ness between these two on one hand and a pair of Malayan 

 bears on the other hand. 



