APPENDIX I 



Pairing (catitinued) 

 Torsion Pairing, non-homologous association at pachytene which 

 releases a torsion without satisfying an attraction, when it occurs 

 in continuance of homologous association. Dariitigton 1935. 

 ToucH-and-Go Pairing, momentary pairing, especially of sex 

 chromosomes, at second division of meiosis in Hemiptera of the 

 hetcrogametic sex. 



Pangenesis, the theory that the heredity of organisms is determined by 

 the summation of influences from an indefinite number of particles 

 (pangcnes) derived from all parts of the body tissue and variably 

 affected by variations in the environment. Darwin 1868. 



Panmixis, unrestricted Random Mating. Properly excluded by any 

 restriction, but sometimes used where random mating is assumed 

 witliin the operation of a restriction, especially with dioecy in 

 animals. Weismann 1895. 



Parameter, a quantity necessary for the specification of a Population. 



Par AS YN apsis, the association of chromosomes side by side observed at 

 zygotene and pachytene, as opposed to their alleged (1905-193 5) 

 end-to-end association at this stage, or Telosynapsis. Wilson 1912. 



Parthenocarpy, the development of fruit without seed as the result 

 of (rt) lack of pollination, with or without artificial stimulation, 

 {h) lack of fertilization, i.e. by incompatibihty or gametic stcrihty, 

 or (c) lack of embryo development, i.e. by zygotic sterility. Noll 1902. 



Parthenogenesis, Apomixis in which the egg cell develops into an 

 embryo. May be facultative, obHgatory, or cyclical. Oiven 1849. 

 Arrhenotocous Parthenogenesis, male-producing (and facultative) 



haploid parthenogenesis as in Haplo-Diploid Sex determination. 

 Diploid (Somatic) Parthenogenesis, in which meiosis fails as well 



as fertilization. 

 Haploid Parthenogenesis, in which meiosis is successful and the 



embryo haploid. 

 Male Parthenogenesis, that in which the male nucleus entering the 



egg cell gives rise to the embryo, without the egg nucleus. 

 Thelytocous Parthenogenesis, female-producing diploid partheno- 

 genesis. 



Patroclinal Inheritance, v. Inheritance. 



Patrogenesis, Male Parthenogenesis. 



Pedigree, table of ancestry or of posterity. 



Penetrance (of a gene), the proportion of individuals of a given genetical 

 constitution in a given population in which the effect of the gene 

 concerned phenotypically distinguishes them from those bearing its 

 allelomorph. Timofecff-Rcssovsky 193 1. 



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