Mat 24, 1907] 



SCIENCE 



829 



I have this year (1905) the first generation 

 of the hybrids, and all the crosses behaved in 

 the expected waj except those in which the 

 ' White flageolet ' entered as one of the par- 

 ents. The crosses between black and brown, 

 black and yellow, and between brown and 

 yellow showed in every case the complete 

 dominance of the darker pigment over the 

 lighter. Thus, the first-generation hybrids be- 

 tween black and brown beans and those be- 

 tween black and yellow were in every case 

 indistinguishable in color from the black 

 parent, whether the black bean supplied the 

 egg or the sperm. Similarly the hybrids 

 between the brown and yellow were in each 

 case not to be distinguished from the brown 

 parent. But the crosses between each of these 

 three pigmented varieties and the ' White 

 flageolet ' gave F^ hybrids so different from 

 either parent that, if unknown, their origin 

 would never be guessed. These seemingly 

 anomalous hybrids were quite indistinguish- 

 able from one another, whether the pigmented 

 parent was black, brown, or yellow. They 

 were characterized by a dark purple pigment, 

 and by an aggregation of the pigment-bearing 

 cells to form a mosaic or mottled surface. 

 Although these hybrids were quite unexpected, 

 it was recalled that Tschei-mak" had secured 

 similar results in a number of cases, and 

 Emerson' describes them also in crosses be- 

 tween 'Ultra' and 'Navy,' this being pre- 

 sumably the very same cross that I present 

 here as ' Ne plus ultra ' X ' White flageolet.' 



Very similar phenomena have been seen by 

 Tsehermak,* Bateson,' and Lock' in peas, by 

 Tschermak* and Bateson" in stocks, by Bate- 



' Tsehermak, E., ' Weitere Kreuzungsstudien an 

 Erbsen, Leukojen und Bohnen,' Zeitschr. Landw. 

 Versuchsw., 7: 533-638, 1904. 



•Emerson, R. A., 'Heredity in Bean Hybrids,' 

 Ann. Rept. Agr. Exp. Sta. Nebraska, 17: 33-68, 

 1904. 



* Tsehermak, loc. cit. 



'Bateson, W., Saunders, Miss E. R., Punnett, 

 R. C, 'Experimental Studies in the Physiology 

 of Heredity,' Second Report to the Evolution Com- 

 mittee of the Royal Society, London, 1905. 



son'^ in sweet peas, by Correns' in Mirahilis, 

 by Cuenot^ in mice, and by Castle' in guinea- 

 pigs. It is not because of the newness of the 

 phenomenon, therefore, that I draw attention 

 to the subject, but for the purpose of dis- 

 cussing the phenomenon of latency in the light 

 of the accumulated data. 



The appearance of hereditary characters 

 which are not traceable to the immediate an- 

 cestry offer the most difficult problems with 

 which the student of heredity must deal. 

 These characters may be recognizable as hav- 

 ing belonged to the more remote ancestry 

 of the form in question, i. e., they are atavistic, 

 or they may be wholly new. Sometimes they 

 occur under known conditions, at other times 

 there is no clue to the causes upon which they 

 may depend. 



These bean hybrids which possess characters 

 not seen in either parent furnish good ex- 

 amples of latency and if we can determine 

 whence the new characters came we shall be 

 far advanced toward a correct conception of 

 latency. Taking, for instance, the hybrids 

 between the yellow and white and between the 

 brown and white, two characters may be recog- 

 nized as new, viz., the dark pigment and the 

 mottled color-pattern. The fact that the very 

 same characters appear in the hybrid off- 

 spring, no matter what the character of the 

 pigmented parent, leaves little doubt that both 

 of these new characters are traceable to the 

 white parent, and we should seem to be war- 

 ranted in saying that this white bean con- 



" Lock, R. H., • Studies in Plant Breeding in the 

 Tropics,' Ann. Roy. Bot. Gard. Perideniya, Z: 299- 

 356, 1904. 



' Correns, C, ' Ueber Bastardirungsversuche mit 

 Mirabilis Sippen,' Ber. d. d. Bot. Ges., 20 : 594-609, 

 1903; ' Zur Kenntniss der scheinbar neuen Merk- 

 male der Bastarde. Zweite Mittheilung iiber Bas- 

 tardirungsversuche mit Mirabilis Sippen,' Ber. d. 

 d. Bot. Ges., 23: 70-85, 1905. 



• ChiSnot, ' Le loi de Mendel et I'hergdit^ de la 

 pigmentation chez les souris,' Arch. Zool. exp4r. 

 et g6n., — : 27, 1902; ' L'hgrgditg de la pigmenta- 

 tion chez les souris' (2me note), Arch. Zool. 

 expir. et g6n., 4 Se., 1: 33-41, 1903. 



' Castle, W. E., ' Heredity of Coat-characters in 

 Guinea-pigs and Rabbits,' Publ. Carnegie Institu- 

 tion of Washington, No. 23, 78 pp., Feb., 1905. 



