160 HEREDITY AND ENVIRONMENT 



from different packs have slightly different 

 values nor are half of the cards taken from one 

 pack and half from another at every game, but 

 this is just what happens in the shuffle and 

 deal of the chromosomes. Because of the mix- 

 ture of chromosomes from distinct individuals 

 in every generation, each of which has its own 

 peculiar value, the game of heredity becomes 

 vastly more complex than any game of cards. 



This illustration may serve to make plain 

 the fact that in the process of maturation and 

 fertilization there is this shuffle and deal of 

 the chromosomes, with the result that every 

 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 



