Live Stock Breeders' AssociaUo7i. 93 



Figure 3.— 2ND GENERATION OF BROWN X BLUE EYES. 

 Br-Browii; Bl-Blue. 



fr. F. & Br. fr. M.-BrBr. 



fr. F. & Bl fr. M-BrBl. 



fr. F. & Br fr. M-BrBl. 



fr. F. & Bl fr. M-BIBI. 



(1) Brown eyes from the father and brown eyes from the 

 mother. This group is homozygote for brown eyes. 



(2) Brown eyes from the father and blue eyes from the 

 mother. 



(3) Blue eyes from the father and brown eyes from the 

 mother. 



(4) The last group inherit blue eyes from the father and 

 blue eyes from the mother. Being homozygote for the blue they 

 will be blue-eyed. 



Each of these four cases is equally likely to occur. The first 

 three of them give brow^n eyes, the last blue ; hence, on the average 

 of a large number of such families, three-fourths of the children 

 will be brown-eyed and one-fourth of them blue-eyed. Many of you 

 will know families in which this law is illustrated. It must be 

 remembered, however, that in such families all the children may 

 inherit either brown or blue from both parents, but such cases 

 will be rare. It is possible from the law of probability to calculate 

 in what proportion of such families any particular combination of 

 brown and blue eyes will occur. 



Let us now return to the case of the Imperial Primrose. This 

 beautiful purple flower originated in a cross between a red and a 

 white variety, the heterozygote being purple. Now, when this 

 purple plant produces ovules and pollen, half the ovules carry the 

 red character and half white. Likewise, half the pollen carries 

 the red character and half the white. The chance union of these 

 pollen grains and ovules covers the same four cases we have con- 

 sidered above in the case of eye color. One-fourth of the seeds 

 produced are homozygote for red; one-half of them are heterozy- 

 gote; the remaining fourth are homozygote for white. We can 

 now understand why this primrose, grown and sold by an English 

 florist for a period of fifteen years, always produced some red, 

 some white, and some purple progeny. Generally speaking, one- 

 fourth of the seed produced red flowers, one-fourth white, while 

 half of them reproduced the beautiful Imperial Primrose (Blue 

 Andolusious). 



Experience has shown that it is impossible to fix the type of 



