158 



GENETICS IN RELATION TO AGRICULTURE 



with the factor for yellow body color and they give identical linkage 

 values with the other factors in this group. Since the factors occupy 

 identical loci in the homologus chromosomes not more than two can 

 occur in the same individual at the same time. This fact was demon- 

 strated in the breeding tests applied above. 



Other cases of multiple allelomorphism are known to occur in a large 

 variety of species. In the silkworm there is apparently a series of 



AB 



BC 



AC 



Expectation 

 Actual Numbers 21 



Fia. 74. Chart showing results of a continued series of pedigree experiments with 

 Paratettix involving types A, B, and C. (After Nabours.) 



multiple allelomorphs concerned in the production of larval patterns. 

 As Tanaka has shown there are four larval patterns, moricaud, striped, 

 normal, and plain. Each of these colors is allelomorphic to the other 

 three and moreover they all apparently display the same linkage values 

 with the pair of factors for yellow and white cocoon color. Like the 

 multiple systems in Drosophila they give no new types by recombination 

 when crossed. 



Multiple Allelomorphs in the Grouse Locust. A very striking series of 



