Principles of Heredity 191 



tains some doubts, and, it will be remembered, cautions his 

 reader that of his exceptions some may be self-fertilisations, 

 and some did not germinate*. Truly a slender basis to 

 carry the coming structure ! 



But Professor Weldon cannot be warned. He told us 

 the "law of dominance conspicuously fails for crosses 

 between certain races." Thence the start. I venture to 

 give the steps in this impetuous argument. There are 

 exceptions t a fair number if we count the bad ones there 

 may be more must be more are more no doubt many 

 more : so to the brink. Then the bold leap : may there 

 not be as many cases one way as the other ? We have not 

 tried half the sorts of Peas yet. There is still hope. 

 True we know dominance of many characters in some 

 hundreds of crosses, using some twenty varieties not to 

 speak of other plants and animals but we do know some 

 exceptions, of which a few are still good. So dominance 



* In his latest publication on this subject, the notes to the 

 edition of Mendel in Ostwald's Klassiker (pp. 60 61), Tscherrnak, 

 who has seen more true exceptions than any other observer, thus 

 refers to them. As to dominance: "Immerhin kommen vereinzelt 

 auch ziceifellose Falle von Jlerkmalmischung, d. h. Uebergangsformen 

 zwischen gelber und griiner Farbe, runder und runzeliger Form vor, 

 die sich in weiteren Generationen wie dominantmerkmalige Misclilinge 

 verhalten." As to purity of the extracted recessives: Ganz vereinzelt 

 scheinen Ausnahmsfalle vorzukommen." 



Klister (22) also in a recent note on Mendelisni points out, with 

 reason, that the number of "exceptions" to dominance that we 

 shall find, depends simply on the stringency with which the supposed 

 "law" is drawn. The same writer remarks further that Mendel 

 makes no such rigid definition of dominance as his followers have 

 done. 



t If the "logician-consulting-partner" will successfully apply this 

 Fallacia acervalis, the " method of the vanishing heap," to dominant 

 peas, he will need considerable leisure. 



