INEQUALITIES IN HOMOLOGOUS CHROMOSOMES | ear 
variety. That something of this nature has occurred, we are 
inclined to believe from the fact that the golden variety is simply 
a plant which lacks chlorophyll in small variegated patches over 
its surface, whose color is therefore due to this condition. In the 
cases here given possibly there is a law at work correlating the 
amount of material that may be lacking from a chromosome 
with the recessiveness or dominance of the trait resulting in the 
organism. <A defective chromosome may continue to give a 
trait which is recessive to the normal condition until the de- 
fectiveness of the chromosome reaches that point where its 
deficiency becomes so great that the homozygous zygote cannot 
develop. At that point the defect becomes dominant to the 
normal condition and individuals can exist only in the hetero- 
zygous or normal condition. 
It is strange that yellow should be dominant in mice while 
in most other species of domestic animals it is recessive. This 
may be due to the position of the yellow determinant along the 
chromosome. In most species it may be thought of as lying 
near the end of the chromosome and accordingly could be dropped 
very easily, causing little disturbance and giving a recessive trait. 
In the mouse it may be conceived of as lying farther from the 
end of the chromosome. On dropping enough of the chromosome 
to cause yellow, a greater disturbance would be created and the 
defective trait resulting would accordingly be dominant to the 
normal trait. JI make this as a suggestion merely. 
The chances for such abnormal divisions are limited by the 
number of pairs of chromosomes in the species and by the vary- 
ing amounts which may be dropped from each chromosome 
in each ease. In guinea-pigs the number of pairs is twenty- 
eight (Stevens 711). The chances for abnormal divisions in 
guinea-pigs are therefore large. Where the number of chromo- 
somes is small the chances are smaller. The amount that may 
be cut off from each individual chromosome might vary enough 
to give several varieties due to the variation in this respect 
in one pair of chromosomes. The same might be said of each 
of the twenty-eight pairs in guinea-pigs. Any of these varying 
conditions in a single pair of chromosomes might combine with 
