174 _ Heredity and Environment 



more than two suits of chromosomes, one of which is maternal 

 and the other paternal. 



To carry out this comparison in the case of the maturation of 

 the human sperm where there are only 47 chromosomes it is 

 necessary to take another pack and discard an additional card, say 

 the queen of clubs ; then in the union of corresponding red and 

 black cards into pairs the queen of hearts unites with the queen 

 of spades, but the queen of diamonds remains alone, and when the 

 cards are dealt into two hands as before one hand will contain 

 24 cards and the other 23. 



If now we complete this comparison by extending it to what 

 takes place in fertilization we must take one hand from each of 

 these deals and put them together into one pack ; this pack would 

 contain cards of every denomination from ace to queen but there 

 would be varying numbers of red and black cards and a mixture 

 of cards from two distinct packs. In no game of cards 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 mixture of chromosomes from dis- 

 tinct 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. 



Germ Cells as Specific as Persons. — This conception of the spe- 

 cificity of every germ cell, as well as of every developed individ- 

 ual, 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, 



