S. V. Haklani) 



lo: 



It riMiiaiii.s ii(»\v t«i i*oiiMi(l«T thr n>Hiilts in tin- li>;l)t <>! Spiliimurh 

 hy|Hithosis that in a rrtww U'twtM'n Solid and Small r\f two laetoix 

 W and H an* roncrrnttl. Kmni tin* F,j rrsnlUs «»f ('msN I it was himmi 

 that iUv nitii* of H U» h was 4M: 1*0 instrad «>( :{ : I, and that this 

 (i(*viatiun hsi to a rorn'.s|H»ndin^ dtviatinn in thr nitin iMtNsrrn thrfnur 

 types. Fnun thr alxivr sunnnarv nf thr f", n-snlts it is rvi<lrni that 

 thi» nititi of H to h is a^ain very ahnonnal while tin- ratio of W In w is 

 of thi' nonnal :i — I tyiH'. 



Art'onlinij to Spillinan s hypothesis the L^enotyjHs appeaiin^^ in F. 

 would Ih' as follows : 



MiiniiijtyicoUK 

 WWHH Solid 

 WWhh WatKoii 

 wwHH Holstein 

 wwhh Siimll ovo 



HoternzyKdTiK 

 wwhH Holstein throwing' MI: ISK 

 wWhh Wiitrtoii tljrowink' HH' : 1.S7-: 

 wWhH Solid throwiriK 9S : AW : MI : l.S/-; 

 wWH H Solid throwing '^^ : 1 "' 

 WWhH Solid throwing •^S : 1//. 



Thus <»f' evi'iy }> Solids. I shimld breed true, 4 should be dihybrid, 

 2 should be inonohybrid {S:H), and the remaining two should be 

 monohybrid {S: W ). C«»mpare the actual facts. The number of /'', 

 tamilies from F.. Solids wjvs 44. Of these 6 bred true, 18 were dihybrid, 

 5 weix^ monohybrid (.S: W ), and 15 were monohybrid (S:H). The 

 coiTes{X)nding exjX'cUition in each case is 49, 19*6, 9*8, and 98. The 

 proportion of homozygous and dihybrid families is seen to be well in 

 accordance with expectation, but there are three times as many families 

 segregjiting into Solid and Holstein as into Solid and Watson. Further 

 if this cross were a simple c<ise of the inheritance of two factors it would 

 be found that the ratio of pure to heterozygous Holsteins would be 1 : 2. 

 This is not so. Out of 22 families grown from F. Holsteins, 12 segre- 

 gate and 10 are pure — a result which indicates that another hypothesis 

 must be sought to explain these facts. 



Imagine that the Solid parent instead of being of the constitution 

 WWHH wjis WWH,H,H,H,, i.e. that it contained two factors each of 

 which could produce the Holstein pattern. And suppose also that each 

 Holstein factor could produce the Solid pattern when in assijciation 

 with th<' Watson fact«>r. The types appearing in the F., of the cross 

 WWH,H,H,H, by wwh.h.hA w(nd(l then be: 27WH,Ho(Solid), 9WH,h, 

 (Solid), 9Wh,H, (Solid). 9wH,H, (Holstein), riWh.h, (Watson). :3wH,h., 

 (Holstein), 8wh,H., (Holstein) and lwh,h., (Siiiail eye). 



The ratio between the four types would be 4-5S : lUV : \^)JI : 1^7i. 

 Of the 45 Solids 7 would breed true, 14 would throw N and //, 8 would 

 thn^w S and W. and the remaining Hi would throw all four types. 



