78 THE MENDEL JOURNAL 



have a bias to one or other of the homozygous char- 

 acters — that is, tend to become sprinters or stayers — 

 may possibly be due to a variabiUty in the number of 

 chromosomes which carry the phylogenetically later 

 developed staying character. This, of course, is a 

 purely speculative hypothesis. Walker has endea- 

 voured to show that older or racial characters are 

 carried by the cytoplasm of the gamete, and the later 

 ones by the chromosomes.* Let us tentatively apply 

 this theory to the two muscle characters in the race- 

 horse. Underlying, as it were, the factors which 

 produce the dark fibre we should have an ever-present 

 factor for the pale fibre carried by the cytoplasm of 

 the gamete, for it is inconceivable that the presence 

 of the pale fibre could be alternative to its absence, as 

 this would entail that a horse might be born without 

 voluntary muscles. If, however, the entities making 

 up the unit character for the dark fibre were carried 

 by the chromosomes, the presence and absence theory 

 fits in remarkably well. The presence in the chromo- 

 somes of these entities forming the unit character of 

 red fibre would be alternative to their absence. 

 Therefore, during the reduction of the chromosomes 

 from twenty-six to thirteen, which takes place prior 

 to the maturation of the gamete, the presence factor 

 would enter some chromosomes, but not others. The 

 greater the number of chromosomes carrying the 

 staying factors of the red fibre, the greater may be the 

 intensity of the character manifested in the soma of 



* Walker, C. E., " Hereditary Characters and their Mode of Trans- 

 mission." 1910. 



