160 GENETICS IN RELATION TO AGRICULTURE 
ears with white cobs and variegated grains and ears with red cobs and 
white grains. None were produced which bore ears having the F; 
combination, red cob and variegated grains, and on the other hand 
none were produced showing the reverse recombination, white ears and 
white grains. 
This series of multiple allelomorphs is perhaps the most striking one 
known and displays just as unique relations as does that series in Parat- 
tetix. For considering only red vs. white alone in these characters 
there are sixteen possible combinations which would give pure breeding 
races. Besides this, however, the red, particularly of the pericarp, 
may be modified in many different ways with’ respect to shade and 
distribution, apparently without altering the relations of the factors 
involved to the allelomorphic system, so that the number of possible 
combinations is considerably greater. Emerson has studied the in- 
heritance of a large number of these types and so far they all may be 
consistently explained on the hypothesis of multiple allelomorphs but 
the data are not as yet extensive enough to establish this interpretation 
beyond any doubt. 
The general nature of multiple allelomorphism is attested to by its 
occurrence in widely separated species of animals and plants. Its 
occurrence in Drosophila, the silkworm, Parattetix, and maize has been 
noted above. Besides these Morgan has pointed out that cases are 
known in rabbits and mice among animals, and in Aquilegia, Lychnis, 
and the bean among plants. In rabbits the factors concerned are three, 
those for self-color, Himalayan pattern, and albinism. In the mouse 
apparently four factors make up a similar system, namely those for 
yellow, black, gray, and gray with white belly. In Aquilegia the system 
has to do with leaf color and three factors are involved, those for green, 
variegated, and yellow leaf color. Shull’s case in Lychnis has to do 
with sex-determining factors. In the bean the case is somewhat like 
that in corn but the series is less extensive. The system there as re- 
ported by Emerson is green leaves, green pods; green leaves, yellow 
pods; yellow leaves, yellow pods. 
Morgan has brought together the arguments in favor of multiple 
allelomorphism and the following discussion is based for the most part 
upon his presentation. This discussion will serve in a sense as a summary 
of the material dealing with multiple allelomorphism. 
1. Systems of multiple allelomorphs appear always to affect the same 
character. This fact is readily apparent from a consideration of the cases 
which have been cited above. Beyond this the cases often give a series 
of diminishing intensities with respect to the character affected as for 
example, black, Himalayan, and white in rabbits. On this basis, Pun- 
nett has sought to disprove the validity of the hypothesis of multiple 
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