THE CELLULAR BASIS 167 



oosperm and every individual which develops 

 from it is different from every other one. 



This conception of the specificity of every 

 germ cell, as well as of every developed indi- 

 vidual, sets the whole problem of heredity and 

 development in a clear light. The visible 

 peculiarities of an adult become invisible as 

 development is traced back to the germ, but 

 they do not wholly cease to exist. Similarly 

 the multitudinous complexities of an adult 

 fade out of view as development is traced to 

 its earliest stages, but it is probable that they 

 are not wholly lost. In short, the specificity 

 of the germ applies not merely to those things 

 in which it differs from other germs, but also 

 to characters in which it resembles others; 

 in short, to hereditary resemblances no less 

 than to hereditary differences. 



The mistake of the doctrine of preformation 

 was in supposing that germinal parts were of 

 the same kind as adult parts; the mistake of 

 epigenesis was in maintaining the lack of 

 specific parts in the germ. The development 

 of every animal and plant consists in the trans- 

 formation of the specific characters of the germ 



