348 



THE EVOLUTION THEORY 



mixis eight paternal ids would unite with eight maternal ids to form 

 the germ-plasm of the new individual, as is indicated in Fig. 87 by 

 a circle of spheres, of which ten are white and ten black as a sign 

 of their difference. We may think of the figure as representing 

 the ' equatorial plate ' of a nuclear spindle with its ids arranged 

 in a circle. Now, if two organisms of this generation, with two 

 kinds of ids, unite in amphimixis after previous reduction of the 

 ids, we have figure B, in which the paternal ids (pJ) are seen to 



(7JZJ m*f 



p 3 J'X\ 



mV 



m 3 J" 



P 3 r 



mV" 



Fig. 87. Diagram to illustrate the operation of amphimixis on the 

 composition of the germ-plasm out of diverse ancestral plasms or 'ids.' 

 A — .D, the ids of the germ-plasm of four successive generations : A, consisting 

 of only two kinds of ids ; B, of four ; 0, of eight ; D, of sixteen kinds. pJ and mJ, 

 paternal and maternal ids. p 2 J, grandpaternal ; p*J, great-grandpaternal ; 

 p*J, great-great-grandpaternal ids. The marks in the ids themselves indicate 

 their individually distinct characters. 



the left of the line and the maternal ids (in J) to the right, while 

 each semicircle is in its turn made up of two kinds of ids, those 

 of the grandparents (j) 2 J and in 2 J, p 2 J 1 and in 2 J 1 ). The figures 

 C and D show the two following generations, in which the number 

 of identical ids is each time reduced to half, because eight strange 

 ids are again mingled with them ; in C only two ids are still identical, 

 and in D all the ids are individually different, because they have come 

 from different ancestors of the same species. Of course this would 

 only be the case if inbreeding were excluded, because through it 

 the ids of the same forefathers from two or more sides would meet : 

 but prolonged inbreeding is a rare exception in free nature. 



