94 GENETICS IN RELATION TO AGRICULTURE 
example peloric snapdragons with flowers flesh-colored on yellow are 
least frequent, but they all breed true on self-fertilization. In the case 
of the most frequent class, however, the zygomorphic red on ivory only 
one plant in 27 is homozygous for the three factors involved and con- 
sequently would breed true. These are features of Mendelism which 
have a direct practical application. 
Multi-factor Hybrids.—Very few cases have been worked out which 
demonstrate conclusively, that more than three pairs of independently 
Mendelizing characters were involved. Not only are the experimental 
difficulties in such cases too great, but the scientific interest attached to 
them is not considerable. From ascientific standpoint accuracy of analy- 
sis is of chief importance, and accuracy is best attained by working with 
small numbers of factors at a time. 
Little and Phillips, however, have conducted an experiment involving 
four pairs of independently Mendelizing factors in mice. The factors 
and the character expressions which they produce are listed below: 
A—factor for agouti coloration. In this type of coloration the pigment is disposed 
in bands in the hairs giving the peculiar gray or agouti coloration of the wild mouse. 
The allelomorph a conditions a uniform distribution of pigment in the hairs. 
B—a factor for black coat color. In this experiment the allelomorph 6 conditions 
the production of brown coat color. 
D—a factor for intensity of coat coloration. Animals with the factor D were full 
colored, whereas those with d were ‘‘dilute” colored. 
P—a factor for eye coloration. P conditions a dark eye coloration; the allelo- 
morph p= pink-eye color. 
Taste XIV.—Fovur-rotp Factor Secrecation or Mice (From Little and Phillips) 
Phenotype | Formula | Observed | Expected | One en dheoretieal 
Blackagoutin wayne sean ee | ABDP 436 373 | 94.5 | 81 
Block tance Aten MOBDE 127 124 | 27.5 27 
Brown agouti. 2.4 a2 oe: | AODP. 103 | 124 22.3 27 
Dilute black agouti............ ABdP 130 124 28.2 27 
Pink-eyed black agouti........ | ABDp 103 | 124 22.3 27 
Brow eae Cee ee ye ae abDP. 40 | 41 Coil 9 
Dilute brown agouti...........| AbdP 31 41 6.7 9 
Dilute black..................) aBdP ot 41 8.0 | 9 
Pink-eyed black.............. | aBDp 35 41 Gi Noe 
Pink-eyed brown agouti....... | AbDp 38 41 8.2 | 9 
Pink-eyed dilute black agouti...) ABdp 38 41 8.2 9 
Dilute brown.................| abdP 11 14 2.4 3 
Pink-eyed brown............. abDP 12 14 2.6 3 
Pink-eyed dilute brown agouti. .| Abdp 15 « 14 3.3 I) 33 
Pink-eyed dilute black.........| aBdp 17 14 ire |S 
Pink-eyed dilute brown........ abdp 7 5 1.5 | 1 
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