AND PLANTS 99 



once in every two throws ; so that if I know that both dice 

 in the first throw gave more than three points, I may 

 expect that both of them will do so in a dependent second 

 throw once in two trials, instead of once in four. 



Now those of you who know Weismann's theory of the 

 mechanism, if I may use that word for want of a better, 

 by which characters are transmitted from parent to 

 offspring, will recognize that the relation I have estab- 

 lished between my first and my second result with these 

 dice is roughly analogous to the relation he indicates 

 between parent and offspring. 



Weismann supposes that the characters, which a parent 

 can transmit, are represented in the young germ-cell, 

 whether male or female, by a certain number of elements, 

 roughly comparable with the dice I have used. Before a 

 germ-cell becomes ripe, so that it can fuse with another 

 germ-cell of opposite sex, half the elements it contains 

 are thrown out of it by what Weismann considers to be 

 a purely random selection ; so that if the constitution of 

 a young germ-cell be represented by the result of a first 

 throw of my two dice, the random removal of half its 

 determinant elements will be represented by the removal 

 of the white die. When a ripe germ-cell fuses with 

 another of opposite sex, a number of elements, equal to 

 the number it has lost in the process of maturation, is 

 restored to it, and the characters of the embryo are deter- 

 mined by these two sets of elements, one set chosen at 

 random from a young germ-cell of each parent. In 

 making my second result with the dice, I have taken one 

 element at random from the two which determined the 

 first result, this process being roughly analogous to the 

 loss of half the determinants during maturation, and I 

 have restored the original number by adding to the one 

 element which remains from the first result a second 



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