58o APPENDIX III 



Male — — , that in which the male nucleus develops into the nuclei of 

 the embryo. 



Phenotype, the external appearance produced by the reaction of an organism 

 of a given genotype with a given environment. Johannsen, 191 1. 



Polar Bodies, the expelled products of the two divisions of the oocyte nucleus in 

 animals. 



Polarisation, (i) of chromosomes at telophase of mitosis, and later the main- 

 tenance of their proximal parts on the polar side of the nucleus ; (ii) of 

 chromosomes at zygotene, the movement of their ends towards one part 

 of the nuclear surface ; (iii) of centromeres, the initiation of orientated 

 division at metaphase of mitosis. 



Polyhaploid, an organism with the gametic chromosome number, arising by 

 parthenogenesis from a polyploid. Katayama, 1935. 



Polyploid, an organism with more than two sets of homologous chromosomes. 

 The terms used are triploid, tetraploid, pentaploid, hexaploid, heptaploid, 

 octoploid (for octaploid), nonaploid (for enneaploid), decaploid, undeca- 

 ploid (for hendecaploid), dodecaploid and so on. Higher multiples are 

 best referred to as 1j\x, 12X and so on {v. Haploid, Diploid and Tetra- 

 ploid). Winkler, 1916. 



Secondary , a homozygous allopolyploid in which some of the 



chromosomes in the basic set are present more frequently than 

 others. D. and Moffett, 1930. 



Polysomic {v. Trisomic). 



Polytene, of chromosomes in the salivary gland nuclei of Diptera. Koller, 



1935- 

 Position Effect, the differences in effect of two or more genes according to their 



distances apart in the chromosome thread. Sturtevant, 1926. 

 [Post-reduction], the alleged reduction of the number of chromosomes, or 



segregation of differences between partners, at the second meiotic division, 



as opposed to pre-reduction, their reduction or segregation at the first 



division. Korschelt and H eider, 1903. 

 Precocity, the property of the nucleus beginning prophase before the 



chromosomes have divided ; characteristic of meiosis. D., 1931, h and c. 

 Differential , the property of some chromosomes or their parts 



condensing, dividing or pairing in advance of the rest of the complement 



during prophase [v. Text). 

 Pro-chromosome, condensed proximal part of a chromosome, staining during 



the resting stage. V. Heterochromatin. Overton, 1909. 

 Pro-metaphase, stage between the dissolution of the nuclear membrane and 



the congression of the chromosomes on the metaphase plate. 

 Prophase, the stage in mitosis or meiosis from the appearance of the chromo- 

 somes to metaphase. Strasburger, 1884. 

 Prothallium, the gametophyte in the Pteridophyta. 

 [Prothallus], = Prothallium, q.v. 

 Protoplasm, that part of the living organism which is not dead (including the 



nucleus and cytoplasm). Purkinje, 1840 ; Strasburger, 1882. 

 Protoplast, the protoplasm of one cell. Hanstein, 1880. 

 Proximal, of a chromosome, a part that is nearer the centromere than a 



particular other part. 

 Pseudogamy, parthenogenetic development of the female gamete, requiring 



the stimulation of the male gamete. 

 Quadrivalent {v. Univalent). 

 Reduction, the halving of the chromosome number at meiosis and, by 



extension, its genetical concomitant of segregation. Weisniann, 1887. 

 Double , the occurrence of a reductional division at both divisions 



