ON THE AMBIGUITY OF MENDEL'S CATEGOPJES. 



r.Y W. F. 11. WELDON, F.R.S. 



I. Introdudorij. 



In the early part of this year I piiblished an account ol' tln' results obtained by 

 Mendel in bis experiments witb certain races of cross-bred petis, and of the subse- 

 queut attempts to show tbat results similar to bis werc obtainablc in othcr cases*. 

 I See no reason to niodify the Statements I then made. 



Since my articlc appeared tlic Royal Society has published a Report by 

 Mr Bateson and Miss E. R. Saundersf, in which a large number of experiments in 

 cross brceding are dcscribcd; Menders results are re-stated, and most of the observa- 

 tions rccorded are hold to be in substantial agreemcut with Mendels laws. In this 

 Report, and in a separate essay by Mr Bateson |, an altogether new interpreta- 

 tion of Mendels results is suggested, and an issue of considerable importance is 

 raised. 



Mendel says Ihat the races of peas, uscd in his experiments, were observed 

 during several generatious, and were found to iliffer constantlyin certain characters, 

 for exaniplc in the colour of tlieir cotyledons, which was grcen in sonie races, yellow 

 in others. Now "green" and "yellow" are not quantitatively dcfinite terms; each 

 includes a considerable ränge of recognisably different coloui-s, and every known 

 race of peas produces sceds whose cotyledons vary in colour. All that can be in- 

 ferred from Mendels statement, therefore, is, that the ränge of Variation in cotyledon 

 colour, which some of his races exhibited, feil entirely within the ränge of colours 

 called "green," while that of other races feil entirely within the ränge of coloure 

 called "yellow." Mendel accounts for the bchaviour of hybrids between these 

 races, as he duscribes them, by assuming that each hybrid bears gametes, male and 

 female, of two kiuds and in equal numbers, "und diiss diese Keim- und Pollonzollen 

 "ihrer inneren Beschaffenheit nach den einzelnen Formen entsprechen §." The 



• See Jiiomttrika, Vol. i. p. 228. 



t Rcpnrts to Ihe Kvolution Committee : I. Experiments undertaken by IT. Btitefon, F.R.S., aiid 

 MUs E. It. Sauiiders, Uoyal Society, l;i02. 



t MrndiVs Prineiplex nf Ilereditij, a De/iiicf : by W. Biitesou. Cambridge University Press, 1902. 

 § VerUandL d mitiirj'ursch. Verein» Jlruiiii, Jiil. iv. p. 2'J. 



