58 Representation of F^ Generation [CH. 



squares, representing the female gametes or germ-cells, 

 similar cells being placed vertically, thus : 



Similarly the male germs may be represented by four 

 squares : 



Here the similar germs are placed horizontally instead 

 of vertically. If therefore the first set of squares be 

 superposed on the second, all the four possible zygotic 

 combinations are represented, thus : 



Thus there are i TT+2Tt + \tt\ and since T is domi- 

 nant, the visible appearance of /% is 



Z T: it. 



We may next deal similarly with the case of two allelo- 

 morphic pairs, Aa and Bb. We shall now require 16 

 squares. Writing each set of four similar female germs in 

 vertical rows and the corresponding sets of male germs in 

 horizontal rows, keeping to the same order, the sixteen 

 possible combinations are represented. In each square the 



