(6) 



studied, and those which are most favor&ble for showing 

 the inheritance of variations within the clone, if it exists, 

 may be determined. 7/hen this has been done, and not until 

 then, one is in a position to put the question to a fair test. 



There are two ways in which the inheritance of variations 

 within the clone may be determined. The first is a statistical 

 method, making use of the coefficient of correlation. The in- 

 heritance of diversities within the clone is always accom- 

 panied, unless some other factor intervenes, by a significant 

 positive correlation between parents and their offspring. 

 Also, as Pearson (1910) has pointed out, if the size of the 

 coefficient of correlation diminishes as we go back to more 

 and more remote ancestral generations, it indicates that in- 

 i'leritance of variations occurs within single clones. This 

 criterion of a "diminishing ancestral correlation" applies 

 to coefficients of correlation computed either from, a single 

 clone or from a population containing many clones. 



All the more recent investigators have realized, how- 

 ever, that results expressed solely as coefficients oi' eor-- 

 relation are often inconclusive and hard to interpret. In 

 particular, if an experiment extends over a considerable 

 space of time, a gradual change in ervirormental cor-ditions 

 which affect the character studied will simulate a true 

 inheritance of variations in the most perfect manner, so far 

 as the resulting coefficients of correlation are concerned. 



The real teat for the ocurrence of heritable variations 

 within a clone must be the success or failure of an attempt 

 to isolate, by selection, hereditarily diverse groups within 



