l6 Pearl and Bartlett. 



viz., an improvement or benefit following the introduction of "new 

 blood" into a strain which had "run out". May it not be that when, 

 as is the case in ordinary "pure breeding" of animals and plants the 

 allelomorphs segregated in gametogenesis are not widely different from 

 one another, there is a gradually declining degree of precision in the 

 segregation ? And further may not this precision be regained and the 

 allelomorphic character determiners be separated in a degree of purity 

 not known in their "pure-bred" history, in a gametogenesis involving 

 widely differing characters? All this is, of course, mere speculation. 

 One hopes, however, that it may serve to direct attention to the 

 importance of careful and detailed comparison between F., and sub- 

 sequent segregates and original parent forms, in order that more data 

 may be obtained in regard to this phenomenon of "intensification" 

 of allemorphic characters during segregation. 



Starch. The starch content shows the same evidence of segre- 

 gation in Fj as do the other characters. The two starchy classes in 

 F., agree very closely with each other in respect to this character, 

 as do also the sweet classes between themselves. It is to be noted 

 that both starchy and sweet kernels in Fg are below the corresponding 

 pure parents in respect to starch content. This is presumably associated 

 with the fact already brought out that the Fo kernels are higher in 

 sugar content than the pure parents. Sugar and starch content are 

 opposed characters in maize. 



Do the Invisible Chemical Characters Segregate Indepen- 

 dently as Separate Units? 



In what has preceded, only the evidence of a general segregation 

 of chemical characters has been presented. We have now to consider 

 the more difficult and more important problem of whether each one 

 of these is a definite unit character segregating independently of the 

 others. Or do these characters form a general complex which as a 

 whole segregates together? Obviously this is a matter of first rate 

 importance, but it is one which cannot be solved by direct methods. 

 Some consideration will make the reason for this clear. Since there 

 is no distinct and definite relation between the external appearance 

 of a kernel and its chemical composition (except in respect to starch 

 and sugar content) the only basis on which kernels can be sampled 

 for analysis m F, is that of external appearance, which we have used. 

 We can take a random sample of yellow starchy, or of yellow sweet, 



