APPENDIX I 



Nucleus, a cell body constituted by chromosomes, i.e. arising by mitosis. 

 R. Broiim 183 1. 



Null Hypothesis, the hypothesis from which the expectations are 

 formulated for the purpose of a test of significance, v. Significance. 



NuLLiPLEX, condition of a polyploid in which all the chromosomes of 

 one homologous type carry the recessive allelomorph of a particular 

 gene, as opposed to Simplex, Duplex, Triplex, Quadruplex, etc., 

 in which the dominant allelomorph is represented one, two, three, 

 four, etc., times. Belling, Blakcslee and Farnham 1923. 



Ogive, the integral of a frequency distribution. Gallon 1883. 



Ontogeny, the developmental history of an organism. 



Oocyte, v. Mother-Cell. Boveri 1891. 



Oogenesis, development of the egg from the oocyte. 



Oogonium, a cell giving rise to oocytes directly or by mitosis. Boveri 1891. 



Orientation, the movement of centromeres so that they lie axially with 

 respect to the spindle, either as to their potential halves at mitosis 

 (Auto-Orientation) or as to members of a pair or higher con- 

 figuration at meiosis (Co-orientation). Determines Congression. 

 Co-orientation or multiple configurations may be Linear, Conver- 

 gent or Parallel. 



Orthogonal, v. Independent Comparisons. 



Outbreeding, v. Inbreeding. 



Ovum, Egg. 



P, the parental generation of an Fj. 



Pachytene, the double thread, and by extension the stage at which it 

 occurs, produced by pairing of the chromosomes in the prophase 

 of meiosis. Winiwarter 1900. 

 Paedogenesis, the asexual multiplication of sexually immature animals. 

 Pairing (of Chromosomes), the coming together of chromosomes at 

 zygotene (active) or the continuance of their association at the first 

 metaphase (passive) of meiosis. 

 Non-Homologous Pairing, the association of non-homologous 

 segments of one or two chromosomes at pachytene. McClintock 1933. 

 Pairing Segment, v. Differential Segment. 

 Secondary Pairing, the lying of homologous pairs of bivalents 



especially close to one another at meiosis. Darlington 1928. 

 Somatic Pairing, the lying of homologous chromosomes especially 

 close to one another at metaphase of mitosis. 



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