APPENDIX I 



Balance {continued) 



Intra-Chromosome Balance, such a condition produced by the 



adjustment of genes within one chromosome. 

 Genic Balance, such a condition produced by adjustment of the 



proportions of genes. 

 Polygenic Balance, such a condition produced by adjustment of the 

 proportions of polygenes having opposite effects. A balanced set 

 of polygenes within a chromosome is a Balanced Polygenic 

 Combination. Where the balance is acliieved within a single 

 representative of the chromosome, and hence is displayed by a 

 homozygote, it is Internal Balance; and where the balance is 

 achieved by two homologous chromosomes acting together, and 

 hence is displayed by a hetcrozygote, it is Relational Balance. 

 Mather 1941. 

 Secondary Balance, a new balance derived by change in the propor- 

 tion of genes, as in a secondary polyploid, from an old balance, and 

 capable of competing with it. Darlington and Moffett 1930. 

 Balanced Lethals, v. Lethal Gene. 



Basic Number, the number of chromosomes in a Set, represented by x. 

 V. Chromosome Set. 



Basic Type, a chromosome complement of characteristic structure and 

 number which exists throughout a species, variants occurring only 

 as heterozygotes. v. Prime Type. Darlington and Gairdner 1937. 



Bias, a consistent departure of an observed quantity from its proper 

 value owing to error of observation or estimation. 



Bimodal, of a frequency distribution having two Modes. 



Binomial Series, the series obtained by expanding the sum of two 

 quantities to any power, (a -|- b)". 



BiOTYPE, a group of organisms occurring in nature assumed to be geno- 

 typically almost identical. Johannsen 1903. 



Bivalent (Geminus), v. also Univalent. A pair of homologous chromo- 

 somes (partners) united at the first division of meiosis, usually by 

 chiasmata. 

 Ring Bivalent, one with terminal or nearly terminal chiasmata at both 



ends of the chromosomes. 

 Rod Bivalent, one with such a chiasma at only one end. 

 Unequal Bivalent, with the two partners of unequal size. 



Bouquet Stage, zygotene and pachytene in those organisms in which 

 the chromosomes lie in loops with their ends near one part of the 

 wall of the nucleus. Cf. Polarization. Eisai 1900. 



Breed, Variety in domestic animals. 



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