APPENDIX I 



Sterility (continued) 

 Male or Female Sterility, failure of male and female organs, 

 respectively, but not of the opposite sex. 



Strictly, sterility should not include the failure of zygotes to 

 mate effectively, merely owing to unlikeness (so-called Cross- 

 Sterility) or failure of male gametes to achieve fertilization of an 

 egg merely owing to likeness (Incompatibility). 



Stock, an artificial Mating Group. 



Strain, a natural or artificial Mating Group uniform in some particular. 

 Biological Strain, one detected by difference in parasitic adaptation. 

 Sexual Strain (incorrect), in Heterothallic fungi, one differing from 

 others in its incompatibility allelomorphs. 



Structural Change, change in the genetic structure of one or more 

 chromosomes. May be intra-radial or extra-radial with respect to 

 arms; internal, fraternal or external with regard to chromosomes; 

 eucentric or dyscentric with respect to the possession of a centromere 

 or to the direction of a segment in relation to the centromere. 

 Darlington 1929, 1937. 

 Balanced (Reciprocal) Structural Change, Interchange and 



Inversion. 

 Unbalanced (or Non-Reciprocal) Structural Change, Deficiency, 

 Deletion and Translocation. Reduplication is a condition arising by 

 segregation from special types of interchange or by unequal crossing- 

 over, e.g. at the Bar locus in Drosophila melanogaiter. 

 Secondary Structural Change, change in structure resulting from 

 Illegitimate Crossing-over. Darlington 1932. 



Structural Control, v. Genotypic Control. 



Structural Hybrid, v. Hybrid. 



Structure, the potentially permanent linear order of the particles, 

 chromomeres, or genes in the chromosomes, v. Structural Change. 

 Darlington 1929. 



Sublethal Gene, v. Lethal Gene. 



SuBSExuAL Reproduction, v. Reproduction. 



Super-Female, an individual with more X chromosomes than sets of 

 autosomes in Drosophila. Bridges 1923. 



Super-Gene, v. Gene. 



Super-Male, an individual with less X chromosomes than half the sets 

 of autosomes in Drosophila. Bridges 1923. 



Suppressive, of a plasmagene which suppresses the expression of an 

 alternative condition in a particular respect in a hybrid individual and 

 its descendents. Darlington 1944. 



421 



