No. 551] THE MENDELIAN NOTATION 



641 



Of course Castle's scheme of expressing the facts by 

 heterogeneity in the germ cell might serve. He pro- 

 duces increased variability in the second hybrid genera- 

 tion by greater differentiation among the gametes aris- 

 ing from the heterozygote. But one can also describe 

 inheritance of qualitative characters in the same way, 

 and one gains no system by it. It is a return to the type 

 of expression used by Nageli, Naudin and De Lage in 

 pre-Mendelian days. It is simply a trans nomination 

 possessing no advantages. 



Before leaving this phase of the subject, I must speak 

 of Davis's recent fine paper (Amer. Nat., 46: p. 415) on 

 his crosses between (Enothera biennis and (Enothera 

 grandiflora. As I have had the advantage of seeing his 

 cultures many times in the past two years, I am in a fair 

 position to draw my own conclusions as to the meaning 

 of his data. In regard to his F 2 generation from the 

 hybrid plant marked 10.30 L b he says : 



1. In the immensely greater diversity exhibited by the F, generation 

 over that of the F t is clearly shown a differentiation of the germ plasm 

 expressed by the appearance in the F 2 plants of definite tendencies in 

 directions toward the two parents of the cross. This seems to the writer 

 the essential principle of Mendelism and does not necessarily involve 

 the acceptance of the doctrine of unit characters and their segregation 



2. Certain characters of the parent species have appeared in the F a 

 segregates in apparently pure condition, but the very large range of 

 intermediate conditions indicates that factors governing the form and 

 measurements of organs (if present at all) must in some cases be con- 

 cerned with characters so numerous and so small that they can not be 

 separated from the possible range of fluctuating variations. If this is 

 true such characters seem beyond the possibility of isolation and analysis 

 and the unit character hypothesis for these cases has little more than a 



3. Both cultures certainly showed marked progressive advance in the 

 range of flower size, the largest flowers having petals somewhat more 

 than 1 cm. longer than those of the grandiflora parent. There was a 

 similar advance in the size of the leaves and the extent of their crinkling. 

 These progressive advances would seem to demand on the unit character 

 hypothesis either the modification of the old or the creation of new 

 factors. 



4. The absence of classes among the F : hybrids (except for the 



