APPENDIX I 



Non-Disjunction {continued) 



Genetical Non-Disjunction, any result that might be imputed to 

 cytological non-disjunction, ahhough usually arising from the failure 

 of pairing, or from multivalent formation. Bridges 1916. Includes: — 

 Chromatid Non-Disjunction, the passage of the parts of sister 

 chromatids distal to a chiasma to the same gamete at meiosis. Where 

 this occurs in a polyploid it leads to Double Reduction. E. R. 

 Satisome 1933. 

 In an XX-XY systems of sex determination (i'. Exceptions) : — 

 Primary Non-Disjunction, the production of eggs with two or no 



X's by an XX individual. 

 Secondary Non-Disjunction, the production of eggs with two X's 



or a Y by an XXY individual. 

 Equational Non-Disjunction, is chromatid non-disjunction in a 

 XXY individual. 



Non-Homologous Pairing, v. Pairing. 



Non-Reduction, failure of Reduction, v. Ameiosis. 



Normal Deviate, the ratio of an observed deviation to the appropriate 

 or corresponding Standard Deviation as fixed by hypothesis. 



Normal Distribution (Normal Curve of Errors), the limit which 

 is reached either by the Binomial or the Multinomial series where 

 the power is large and none of the summed quantities very small 

 in relation to the power and to one another. This frequency dis- 

 tribution is expected from a series of observations on a variate whose 

 magnitude is affected by a large number of agents having small 

 independent effects. 



Nucellar Embryony, a form of Apomixis where the embryo arises 

 directly from the nucellus. 



Nuclear Sap, the fluid which is lost by the chromosomes as they 

 contract during prophase and which fills the space of the nucleus. 



Nucleic Acid, the product of polymerization of Nucleotides which 

 have either all ribose sugars giving yeast or Ribo-Nucleic Acid, or 

 desoxyribose sugars, giving thymus (or chromosome) Desoxyribo- 

 NucLEic Acid. 



Nucleolus, a body not containing desoxyribose nucleotides and secreted 

 by a specific organizer, gene or super-gene, in the resting nucleus. 

 McCUntock 1934. 



Nucleoprotein, a protein which is combined, or combinable, with a 

 nucleic acid. 



Nucleotide, a chemical group consisting of purine or pyrimidine base, 

 ribose or desoxyribose sugar, and phosphoric acid. 



406 



