THE AMERICAN NATURALIST 



[Vol. XLVI 



It has been questioned whether one has the right to con- 

 tinue to couple characters in large numbers to interpret 

 facts, because by proper coupling one may interpret 

 almost any fact, and place himself in a logically unassail- 

 able position. But this is no reason for not coupling 

 factors as much as one pleases if it is helpful and if all 

 of the facts fit. A propos of this statement I might say 

 that I have recently remade the historical old cross first 

 made byKolreuter in 17 60, Nicotiana rustica X Nicotiana 

 paniculata. These species differ in many details— habit 

 of growth, size, shape and hairiness of leaf, inflorescence, 

 and size and shape of flower and fruit. Both of the pa- 

 rent species have been reproduced exactly from a par- 

 tially fertile Y 1 in a total number of less than 200 F 2 

 plants. One may formulate an hypothesis of selective 

 elimination of gametes combined with selective fertiliza- 

 tion that helps to describe the facts, but unless large 

 numbers of factors are coupled together I believe it to 

 be impossible to account for all the facts by the usual 

 Mendelian notation. 



Before leaving this subject it might be mentioned that 

 Bateson's theory, originated to account for partial coup- 

 ling, keeps the idea of factors segregating from their 

 absence, but instead of A and a being formed in equal 

 quantities as in "regular" Mendelian notation, they are 

 to be formed in series represented by the scheme n—lAB : 

 lAB:laB:n — lab. I do not believe one should hasten 

 to accept this description, although Bateson's F 2 gen- 

 eration facts certainly fit and have been recently sup- 

 ported by Baur. My reason for making this statement 

 is that as yet Bateson's F 3 facts do not fit the theory. 

 Some of them would even make necessary two or more 

 different kinds of factorial distribution in the same plant 

 varieties. On this score the helpfulness of our notation 3 



•Here is a good illustration of the Mendelian notation as a concept. 

 Supposing the gametic distribution n — 1AB : lAb : laB : n — lab were to 

 fit all the facts in the case, then no one could object to its use. If it were 



ever, the scheme no longer fits the facta and must be abandoned. 



