14 



THE AMERICAN NATURALIST [Vol. XLVlI 



The same scheme might be followed by using the small 

 letters for the factors in the original red eye : thus red = 

 pve; and the capital letter for the corresponding factor 

 in the mutant ; thus, vermilion = pVe, etc. A disadvantage 

 of this scheme is that the large letter now stands for a 

 recessive condition and the small letter (its allelomorph) 

 for a dominant condition. Usage has, however, made us 

 accustomed to interpreting a large letter as a dominant, 

 its corresponding recessive (its allelomorph) by a small 

 letter and therefore the plan first suggested seems more 

 desirable. It is with much reluctance that I suggest this 

 change in our present nomenclature. It has become nec- 

 essary, however, in the case of the Drosophila to find 

 some way to represent consistently those cases in which 

 three or more factors are involved in the same organ. 

 The change is not one of any theoretical importance, but 

 a practical necessity for all cases of this kind. When one 

 new character is contrasted with the original one, Men- 

 del's way may still be the simplest and easiest way of 

 formulating the results, and will, no doubt, be followed. 

 When two new characters are involved the formula of 

 presence and absence is a sufficient way of representing 

 the symbols. But when new mutations are appearing 

 some other plan must be adopted. The one here sug- 

 gested has at least two merits: it is as easy to use as 

 either of the foregoing for one and for two characters, 

 and can also be utilized when any number of further 

 mutations appear in the same organ. 



The scheme applied to body colors is as follows : Two 

 mutants arose, yellow and black, and by recombination, a 

 "brown" or yellow-black fly was obtained. The symbols 

 would be wild fly = YYBB, jellow=yyBB f blackFF&fc, 

 and yellow-black yybb. Two other mutations in body 

 color have appeared, both dark, one is called ebony, eb 

 and the other sable, ,s. When brought in connection with 

 the preceding mutation the gametic symbols would be : 



Wild fly YBEhS 



Yellow yBE»S 



