()41] sUOBLIR ARlICLLs {\n ni^CLbSIO\ 557 



tint tl.( 1 1 N u, 1 1 Its n, I ,n ,1- tlu combiru d ranges of P, 



l.unr plu. ' I t MM. . un 'K . <iu il ffcct 



What \\<>s piviuaturc sevcji vcars ,i<i(> iniglit bo conceivably 

 no longer premature, ot course, but since tlie basis upon which 

 Dr. Castle now proposes to estimate the number of such plural 

 factors m specific crosses involves the sam(? tallaeios which made 

 previous attempts untenable, it is needful to reiterate that noth- 

 ing m the evidence justifies the belief that this new plan will give 

 any sort of approximation to the actual facts. Nevertheless, the 

 method proposed by Ca,stle may be expected to have a certain 



It is absurd to suppose that the height of a man will be as 

 much affected, severally, bv the factors which increase the thick- 

 ness of the scalp, as by those which affect the length of the long 

 bones of the legs ; or that factors which produce changes m the 

 number of internodes of a plant will generallv add severally the 

 same increment to the stature of the plant as will factors which 

 increase the length of some or all of the internodes. Castle rec- 

 ognizes this weakness, but seeks to minimize its importance and 

 declares that "no other assumption will permit of a general 

 treatment of blending inheritance. ' ' He means, of course, merely 

 that on no oilier ])asis can a «j(Micralized matlieinaticnl scheme be 

 developed sudi ns l]i;it wliidi lie li;is lirrr prrsiMil I'll. 



which are equallv uiiwaiT;niir,| ana wliiHi will proloundlv affect 

 the validity of the courlnsicns aiTivcd at. 



For example, the two si rains inaicd lo-ivihcr ai-e supposed to 

 stand at the two extremes ot the total potential genetic vari- 

 ability m their progeny and all of the determiners are assumed 

 to be additive in their effect, so that if we let the factors be repre- 

 sented m the usual manner bv letters, the lesser parent must have 

 the fonnnia XXnahhauJ,], dT .... whdc tlio laravr parent oc- 

 . npi . til tli, I \ 1.111 \ \ 1 \niU ( ni>l I } r it ne-d 



scan-Hv hr pointed out lliat whil,' mu-I. a situatmn niight be 

 realiz.Ml in sumo sp.M-iHc ras,. it rouM not ho -vihTallv true, and 

 tlio irtvatoi- tlir riiinilMT nf fartors invohvd in anv specific cross, 

 llio |,.s;s likrl\- would It h.' iliat tiio lar-tT parent would possess 

 tlioni all and tlio lesser paronr iionf. In niv paper, referred to 

 above. I said m regard to this point f p. I;i2) : 



