APPENDIX I 



Cytoplasm, the Protoplasm other than the Nucleus. Strasburger 1882. 

 Cytoplasmic Inheritance, v. Inheritance. 



Dauermodihcation, a lasting heritable change, presumably cytoplasmic, 

 produced by treatment. Jollos 191 3. 



Daughter Chromosome, v. Chromatid. 



Dehciency, loss of a terminal acentric segment of a chromosome. Often 

 used to include Deletion, v. Structural Change. Bridges 191 7. 



Degree of Freedom, a comparison between items within a given body 

 of data, independent of other comparisons used in the analysis. 

 Number of Degrees of Freedom, the number of independent com- 

 parisons that can be made within the body of data. 



Delayed Inheritance, v. Inheritance. 



Deletion, loss of an intercalary acentric segment of a chromosome. 

 V. Structural Change. Painter and MuUer 1929. 



Descendance, all the individuals descended by sexual reproduction from 

 a single individual or particular mating pair. 



Determinant, an element in the cell postulated to control heredity and 

 development. The precursor of the gene concept. Weismann 1891. 



Developmental Genetics, the study of the operation of genes during 

 development. 



Deviation, departure of a quantity (derived from one or more obser- 

 vations) from its expected value. 

 Standard Deviation, the distance on the abscissa of the point of 

 inflection (maximum slope) from the mean in a normal curve. 

 Generahzed as the square root of the Variance. Called the Standard 

 Error when the deviation can be regarded as an error, e.^. with 

 estimates of parameters. 



DiAKiNESis, the last stage in the prophase of Meiosis, immediately before 

 the disappearance of the nuclear membrane. Haecker 1897. 



DiALLEL Crossing, the system where each of a number of males is mated 

 to each of a number of females. 



Dicentric, of a chromatid or chromosome having two Centromeres, 



Differential Afhnity, the failure of two chromosomes to pair at meiosis 

 in the presence of a third, although they pair in its absence. Dar- 

 lington 1928. 



Differential Segment, a block of genes in respect of which two pairing 

 chromosomes difler, in a permanent hybrid (Sex and Complex 

 Heterozygote) in contrast to a Pairing Segment where they pair 

 and cross-over, and are therefore homologous. Darlington 193 1. 



387 



