HETEROZYGOTE FORMS 



183 



splashed white are splashed white. The following 

 scheme of inheritance illustrates the phenomena 

 described : 



I (zygote) 



1 (gametes) 



2 (zygote) 



2 (gametes) 



3 (zygote) 



3 (gametes) 



4 (zygote) 



blue heterozygote 



black and white 



I 



I black-black 2 black-white I white-white 



(blue heterozygote) 



black black white 



black white white 



I 



black 



i black 2 blue I white 



black\ 

 black f 



white 



/white 

 \white 



all blue heterozygotes 



A case which is closely similar to that of the An- 

 dalusian fowl is afforded by the cross between Primula 

 sinensis and Primula stellata. 



P. sinensis crossed with P. stellata gives rise to a 

 type which is different from either parent, being in 

 some respects intermediate between the two. The 

 hybrid is so distinct that a special name has been given 

 to it, and the new type is known as P. pyramidalis. 

 So far it has been found impossible to obtain a strain 

 of P. pyramidalis which will breed true. On self- 

 fertilization the offspring are found to show the types 

 of P. sinensis, P. pyramidalis, and P. stellata in the 

 ratio of i : 2 : i. 



Cases like the above illustrate the essential part of 



