W. i; l{. Wkldon 45 



issuc raised by Mr Batuson aiiil Miss Saundcrs concenis Ihc iiieaiiiiig wliicli it, is 

 ncccssary, in tlic light of kiiown l'acts, to givo to this exprcssioii. 



The rc>sult, described hy Mendel, niaybe illustrated by rcfcrenee Lu Uie Cullinving 

 diagram : 



Let AD be a seale i)f' eolour, — a map nf a speetrum, or some similar lliiiig, — of" 

 whieh tlie i'ange AB inelndes tlie variuus shades of green, the ränge CD thosc «f 

 yellow. A race of peas has cotyiedons whose eolour varies, in individual casos, 

 within the ränge AB; a second race has cotyledon.s which vary withiu the ränge 

 CD. If these races be crossed, the hybrid cotyledons are said to fall within the 

 colour-range CD; and the plants to which they give rise will, on Mendels hypo- 

 thesis, produce gametes of two kinds, in ecpial numbers; those of the first kind, if 

 paired, give rise to plants whose cotyledou eolour (and that of their descendants) 

 lies within the ränge AB; those of the second kind, if paired, give rise to descendants 

 whose cotyledon eolour lies within the ränge CD. 



That is to say, the descendants of such a cross fall iuto two group.s, each refer- 

 able, so far as cotyledon eolour is concerned, to the same category as ono of the 

 ancestors used in the original cross. Wc are quite unjustified, from the data given 

 by Mendel or by any of those who follow him, in saying more than this. Thus the 

 green-seeded descendants of such a cross are de.scribed as "green": they are not 

 described, by Mendel or by aiiy of his foUowers, as being of the same shade of 

 green as the particular member of a variable race used in the original cross. The 

 information given is therefore compatible with either of sevei'al tlieories of the 

 Constitution of those gametes in the hybrid frum which " recessive " individuals 

 arise. For anything we are told to the contrary, the character transmitted by such 

 gametes may be a blend of all tho kinds of green exhibitcd by their green-seeded 

 ancestors in various proportions ; or different gametes may revert directly to the 

 eolour of different individual ancestors; or finally all the recessive gametes may 

 transmit the characters of the green-seeded ancestor which took part in the original 

 cross, and of no others. The first two hypotheses involve the belief that the 

 coniposition of gametes of either kind, whether "dominant" or "recessive," is 

 affected by that of a whole series of ancestors. Such belief seemed (and still seems) 

 to me a necessary con.sequeuce of the facts. Mr Bateson and Miss Saunders have 

 however adopted the view that "the [niro dominant and the pure recessive members 

 " of each generation are not merely like, but identical with the pure parents" (I.e. 

 p. 12); and Mr Bateson denounces in no mcasured terms my attempt to regard the 

 inconsistent results obtained by thosc who have repeated Mendel's experiraents as 

 due to diflferences in the ancestry of the races used. 



Mr Bateson fully admits the variability of all races of peas ; and he admits that 

 the ränge of colour-variation in many races is so great that they include colours 

 of both the "green" and the "yellow" category. Nevertheless, he believes that 

 many of these races behave, when crossed, like those described by Mendel. This 



