126 THE AMERICAN NATURALIST [Vol. LIII 



gametic composition turned out to be PpCCaee. He 

 was mated to a pink-eyed tortoise, $734.2,^ whose com- 

 position judging by lier otfspring, must have been 

 ppCiCe^e. This cross may be represented as follows: 



[pCae pCre 



PpCrCrePe \ 

 PpCrCaePe J 



^yed non-y 



^ }p..e.ea„o„.e„o....„.e 



' 



tct: }~-~-"<.»-»- = 



Total 12 



It will be seen that according to expectation there 

 should be equal numbers of '8 different phenotypes. The 

 12 offspring actually obtained are remarkably close to 

 expectation. 



At the time this cross was made the gametic composi- 

 tion of the mother, $73-l-.2, was not definitely known. 

 When, therefore, the two pink-eyed non-extended non- 

 yellows were born one could not be certain that they 

 wore not just ordinary albinos. The oidy definite method 



