So 



MEN DEL ISM 



grain, when these were so vastly outnumbered by 

 normal ones. The evidence in this case suggests 

 that two normal gametes met, that subsequently a 

 radical change occurred in the young zygote, whereby 

 the normal factor \\as somehow obliterated. 



The exact point of origin of few, if any, mutations 



i(i. 17. 



'rhc "cretin '' sweel-pca. 



is so well established as that of the cretin. Never- 

 theless enough is known to show that they frequently 

 occur in the same way — as rare and isolated instances 

 in a strain of normals, and behaving as simple re- 

 cessives to those normals. Evidently wc have not 

 yet found the solution to Plutarch's problem. 



