11. C, PUNNEIT 49 



Nor shotild it be forgotton that more ample data may shew tliese 

 debatable cases to be (^xainplos of partial coupling of very high in- 

 tensity. The appearance of a single Himalayan in F., from the cross 

 of self-colour x albino of an eosin-eyed JJrosophila ex red eye x white 

 would, as Sturtevant admits, invalidate the " Multiple Allelomorph " 

 hypothesis. Gases are now known where the coupling between two 

 factors, though not quite complete, is of very high intensity. In 

 sweet peas for example the coupling between the factor for blue 

 (B) and that for the erect standard (E) is such that in plants hetero- 

 zygous for both flictors, the gametic series must be supf)osed to be 

 127BE : IBe : IbE : r27be. Such plants crossed with be pollen would 

 give but a single specimen of each of the two rarer classes (blue 

 hood and red erect) in 256 plants. If the coupling were of even 

 higher intensity it might easily be regarded as comjjlete unless very 

 large numbers were raised. As time goes on the phenomenon of 

 partial coupling and repulsion is turning out to be a widely spreatl 

 one among animals as well as plants. Whatever the explanation may 

 turn out to be ultimately, it seems reasonable to regard cases of 

 apparent complete coupling as falling into the general scheme until 

 we have definite evidence to the contrai'y. It would appear premature 

 therefore to reject the " Presence and Absence " hypothesis for that 

 of " Multiple Allelomorphs " until we are in possession of facts which 

 compel us to take this step. We certainly do not possess such facts 

 at present. 



I desire here to acknowledge grants of £50 from the Government 

 Grant Committee of the Royal Society during 1913 and 1914. Without 

 them these experiments could not have been undertaken. 



PAPERS REFERRED TO. 



(1) Bauk, E. "Vererbungs- und Bastardierungsversuche mit Autinliiiium. 



II. Faktorenkoppelung." Zeit. f. ind. Abst. u. Vererb. 1912. 



(2) Castle, W. E. " Heredity of Coat Characters in Guinea-Pigs and Kabbit.s." 



Publ. Carnegie Instit., Washington, 1906. 



(3) (and others). " Studies of Inheritance in Rabbits." I'ubl. Canicgiu 



Instit., Washington, 1909. 



(4) Emekson, R. a. "Genetic Correlation and Spurious Allelomorphism in 



Maize." Ann. llep. Nebr. Agr. Sta. 1911. 

 Journ. or Gen. v 4 



