4i8 



BREAKDOWN OF GENETIC SYSTEMS 



Haploids. 



Datura Stramonium 

 Matthiola incana . 

 Nicotiana glutinosa 

 Nicoiiana Langsdorffii 

 Crepis capillar is 



(Enothera franciscana 



Aegilotricum {8x) . 

 Triticum monococcum, 

 Oenothera rubric alyx 

 CEnothera blandina 

 (ii) Due to a Genetic Property 

 Perla marginata ((J) 

 Avena sativa {6x — 2) 

 Nicotiana alata {2x + i) 

 Zea Mays (asynaptic) 

 Drosophila pseudo-ohscura hybrids 



Belling and Blakeslee (1923, 1926) 

 Lesley and Frost, 1928. 

 Goodspeed and Avery, 1929 

 Kostoff, 1929. 

 Hollingshead, 1930 a. 

 Emerson, 1929. 

 Davis and Kulkarni, 1930. 

 Stomps, 1930, a and b. 

 Katayama, 1935. 

 Katayama, 1935. 

 Gates and Goodwin, 1930. 

 Catcheside, 1932. 

 {cf. Section 4). 



Junker, 1923. 

 Huskins, 1928 

 Avery, 1929. 

 Beadle, 1930. 

 Dobzhansky, 1934. 



Nishiyama, 1931. 



All cases of facultative and cyclic parthenogenesis with suppression 

 of the first division [v. Ch. XI). 



B. Double division of univalents (part 



PygcBra hybrids 



Rosa canina 

 Rosa subglauca 

 Raphanus-Brassica 

 Prunus avium nana 

 Saccharum officinarum . 

 Ribes, hybrids 

 Brassica, hybrids 



C. Failure of Spindle ; due to genetic 



Triticum vulgare var. 

 Kniphofia .... 

 Hyacinthus orientalis 

 Zea Mays (var. sterile) . 



D. Due to External Conditions (effect 



Vicia . 



Funaria 



Epilobium 



Gagea 



Liriope, Scilla 



Lychnis 



Triticum 



ial except in the first instance). 



Federley, 191 2, 1931 ; Cretschmar, 

 1928. 



Tackholm, 1922. 



Erlanson, 1929. 



Karpechenko, 1927, a and b. 

 . D., 1930 a. 



Bremer, 1930. 



Meurman, 1928. 



Morinaga, 1929. 

 property. 

 . L. A. Sapehin, 1931. 

 . Moffett, 1932. 

 . De Mol, 1923 ; Stow, 1930. 

 . Beadle, 1932. 

 shown by abnormal treatment). 



Sakamura, 1920. 

 . V. Wettstein, 1924. 



Michaelis, 1926. 



Sakamura and Stow, 1926. 



Shimotomai, 1927. 

 . Takagi, 1928. 



Bleier, 1930. 



(vii) Conclusion. These observations are important in four 

 directions. They explain the origin of polyploids by failure of 

 meiosis. They show the relationship of normal meiosis with its 

 special modifications in apomictic organisms where, as we shall see, 

 the sexual cycle is suppressed. They also show that the metaphase 

 of meiosis, as well as the prophase, is precocious, since the univalent 



