ee W. R. B. ROBERTSON 
these on being crossed with brown, or any animal that contains 
the color factor, will give gray or black, ete., showing the gray 
or black characters to have been present in substance though 
not developed. [If the black be absent, nothing can restore 
it except the addition of black again. There is evidently a com- 
plete absence of the black pigment material from the fur of the 
animal. 
In the varieties of domestic plants many similar cases may be 
given. But before mentioning the color varieties | wish to call 
attention to the cross between the ‘cupid’ and the ‘bush’ variety 
of sweet pea as one of the best examples. The cupid is a dwarf 
plant whose internodes are very short, making the stem cor- 
respondingly short, about 9 to 10 inches. It has the prostrate 
habit, that of lying on the ground, due to the diverging habit 
of the branches. The ‘bush’ variety produces branches which 
do not diverge but grow upright, making a tall bush growing 
42 to 48 inches in height. These varieties, on being crossed, 
produce in the F, generation plants which show a reversion to 
the habit and size of the wild sweet pea of Sicily (Punnett 711). 
They have the long internodes and the long stem of the bush 
variety combined with the prone, prostrate habit of the cupid 
variety. By inbreeding the F, individuals the F, show the tall 
‘bush’ variety, the tall procumbent, the short procumbent or 
original ‘cupid,’ and the short ‘cupid’ bush-like variety. The 
factors concerned are the long internodes versus the short, and 
the procumbent versus the erect habit. The two varieties 
evidently owe their origin to the dropping of one or the other 
of these factors from the germ plasm of the wild type. The 
bringing of them together in the hybrid supplies the lack in both 
races (the ‘cupid’ and the ‘bush’ varieties), the result being the 
wild type. 
In flower color of sweet peas we have a similar case. Most 
white sweet peas breed true to white, but there are two varieties 
of white which on being crossed produce a purple colored variety, 
like the wild Sicilian species. On being inbred, the F, generation 
shows nine of the colored variety and seven of the white. Of the 
whites some breed true, some give a 3.1 ratio, 1.e., three whites 
