No. 551] THE MENDELIAN NOTATION 



635 



If we forget ourselves and begin to speak of unit factors 

 as particles, only a confusion follows similar to that 

 caused by Nageli, Spencer and Weismann. Nothing is 

 gained and even facts are obscured. 



The Scope of Mendelism 

 How far may we carry this conceptual notation? My 

 answer is : just as far as the notation interprets the facts 

 of breeding and is helpful. Interest in the scope of Men- 

 delism is now focused on two phases, complete and par- 

 tial coupling and the interpretation of so-called size char- 

 acters. Complete coupling in the transmission of char- 

 acters apparently non-related has been shown in a large 

 number of cases. Perhaps those best worked out in ani- 

 mals are the sex-coupled or sex-limited characters ob- 

 served by Morgan in Drosophila. In plants, cases ob- 

 served by Emerson and by Bateson and his coworkers 

 are equally clear. Emerson has shown beyond a rea- 

 sonable doubt that the characters he describes are inde- 

 pendent of each other, and can not be represented by one 

 factor. Bateson has recently corroborated the observa- 

 tion on other characters. Besides this phenomenon, 

 Bateson has discovered partially coupled characters. 

 All three of these writers, have subsidiary hypotheses to 

 account for their facts. Bateson, when discussing per- 

 fect couplings, merely says that the characters come out 

 in F 2 coupled in the way they went in in the grandpa- 

 rents, which naturally is only a restatement of the facts. 

 Morgan and Emerson deal in pictures of carrying bod- 

 ies. Both of their theories fit their own facts as they 

 necessarily would. Emerson and, I may say, myself be- 

 lieve Morgan's theory incompatible with that of Emer- 

 son. Morgan believes his theory adequate for both 

 cases. Without discussing the merits of these particular 

 hypotheses I think it is agreed that some characters do 

 go into the Fj generation and come out from it together 

 that are in other cases independent. The importance 

 of the phenomenon is greater than the theory at present. 



