86 THE MENDEL JOURNAL 



Simon," who had sired hundreds of foals., but all of 

 them bays or browns, and never begot a grey until 

 " Postumus," his last foal, icame. We notice that 

 along the whole of the maternal line of "Pontoon's" 

 pedigree (the dam of "Postumus"), there is an un- 

 broken stem of grey (Plate 1). We further notice 

 throughout this stem that every grey mare — 

 "Euxine," " Maid of Wye," " Pontillon," and 

 " Pontoon " — is the offspring of a grey crossed 

 with a bay. That is, every grey horse must have 

 one parent grey. 



Now these and other indications are clearly 

 Mendelian phenomena. "Pontoon," the dam of 

 " Postumus," is a Mendelian heterozygote, or 

 hybrid, carrying dominant grey and recessive brown 

 or bay, and possibly recessive chestnut too. The 

 sire of "Postumus," namely, "St. Simon," has 

 shown by his numerous offsiDring that he is pure 

 for l)ay. 



The mating out of which the unexpected grey 

 colt, " Postumus," was produced, therefore resolves 

 itself into one of "Pontoon," which is DR for 

 grey (D) and bay (R), with "St. Simon" (DD) 

 for bay. Now if grey is dominant, the Mendelian 

 expectation in such a mating is an equal number 

 of heterozygote or hybrid greys (D R) and of bays 

 (DD). And it so happens that a grey has come 

 first. Unfortunately " St. Simon" is dead, and the 

 same pairing cannot be repeated. But it is to be 

 hoped that "Pontoon" may be mated on several 

 occasions to a sire known to be homozygous 



