438 THE AMERICAN NATURALIST^ [VOL. XLII. 



pattern could not exist in both the pigmented and white 

 beans used in these crosses, as in that case the Fj hybrids 

 would have been homozygous with respect to this char- 

 acter and would have been black self-colored instead of 

 purple mottled. In attempting to settle the question as to 

 the origin of this mottled color-pattern I have carefully 

 examined the results recorded by Tschermak and find evi- 

 dence that at least one pure-bred pigmented bean must 

 possess the mottled pattern while another does not. 

 Whether the white beans used by him carried latent M 

 can not be settled at present, but it is now plain that he 

 may have been right in referring the mottling factor to 

 the pigmented beans. My White Flageolet as well as all 

 the white beans used by Tschermak may not have the 

 mottled pattern, and the gametic formula of the White 

 Flageolet should then be written pBm, instead of pBM. 



This question can only be settled by further careful 

 crossing. The evidence derived from Tschermak is as 

 follows: In the cross between "Hundert fiir eine" (light 

 yellowish brown) and "Mettes Schlachtschwert" (white) 

 there was no mottling in the offspring; "Hundert fiir 

 eine" crossed with "Schwarze Neger" (black), both self- 

 colored, gave mottled offspring. Now according to my 

 hypothesis, if "Schwarze Neger" carries the mottled 

 pattern, ' ' Hundert fiir eine ' ' does not have it, and in turn, 

 "Mettes Schlachtschwert" must not have it. If 

 1 i Schwarze Neger, " on the other hand, does not carry the 

 mottled pattern, "Hundert fiir eine" has it, and in this 

 case "Mettes Schlachtschwert" must also carry it. W T e 

 can not say certainly, therefore, that the white "Mettes 

 Schlachtschwert 7 ' does or does not have the mottled pat- 

 tern, but on theoretical grounds either condition would be 

 equally possible. 



Among the corollaries of the explanation here given for 

 the ratio 18 : 18 : 6 : 6 : 16 is not only the fact already given 

 that the mottled pattern may be carried by the pigmented 

 bean invisibly quite as well as by the white bean, but 

 also, since the mottled beans are heterozygous with re- 



