158 HEREDITY AND ENVIRONMENT 



sons which develop from these cells are de- 

 termined in large part by the particular kinds 

 of germ cells which unite in fertilization. 



The behavior of chromosomes in matura- 

 tion and fertilization is like the shuffle and deal 

 of cards in a game, and apparently with the 

 same object, viz., never to deal the same 

 hand twice. To make this comparison more 

 complete suppose that kings be discarded from 

 the pack, leaving 48 cards of two colors, red 

 and black, which we will compare to the 48 

 chromosomes of maternal and paternal origin 

 in the human oocyte ; suppose that in the shuf- 

 fling of these cards corresponding cards of the 

 red and the black suits are temporarily stuck 

 together so that the ace of diamonds is united 

 with the ace of clubs, the queen of hearts with 

 the queen of spades, etc., thus forming 24 red- 

 black pairs of the same denominations. If 

 these cards are then dealt into two hands, one 

 card of each pair going to one hand and the 

 other to the other hand, we will have two 

 cards of each denomination in each hand, but 

 if the cards are dealt indiscriminately some of 

 them will be red and some black. This de- 



