UNBALANCE AND VIABILITY 319 



Similar elimination is found in the breeding of plants and animals 

 that are simply trisomic, either in a whole chromosome or in part 

 of a chromosome (v. Table 50) or in the development of pollen of 

 plants of these types (v. Table 51 and Fig. 103). 



Table 48 



A. Trisomic Organisms showing Differential Action of Chromosomes. 



CEnothera Lamarckiana. de Vries. Cf. Lutz, 1907 b ; Catcheside, 1933, 



1930 ; Emerson, 1935, 1936 [cf. Ch. XII). 

 Datura Stramonium. Blakeslee, 1922, 1928, 1931. 

 Matthiola incana. Frost and Mann, 1924 : M. M. Lesley and Frost, 



1928. 

 Crepis spp. Navashin, 1926, 1930 a ; Hollingshead, 1930 b. 

 Zea Mays. McCIintock, 1929 a ; D., 1934 ; Rhoades and McClintock, 



1935- 

 Solanum Lycopersicmn. Lesley, 1928. 

 Avena. Nishiyama, 1934. 

 Antirrhinum. Propach, 1935. 



Vicia macrocarpa (6) X V. sativa (6) Fg. Sweschnikowa, 1929 b. 

 Secale cereale. Takagi, 1935. 

 Drosophila melanogaster. Bridges, 192 1 b. 



B. Unbalanced Clonal Forms. 



Hyacinthus {2x + 1-14). de Mol, 1923 : D., 19296. 

 Narcissus {2x + i, 2 ; 3;»r + i, 2). Nagao, 1933. 

 Chrysanthemum {6x -\- 3-6). Shimotomai, 1933. 

 Crocus spp. Mather, 1932. 

 Iris spp. Simonet, 1934. 

 Poa alpina. Miintzing, 1932. 



The relative viability of the different kinds of progeny of triploids 

 and aneuploids may be tested. They differ ^rom the normal in 

 two ways : — 



(i) in the size of the fraction of the whole complement which is 

 present in excess, the fraction being in the following degrees : 

 fragment or small chromosome, whole chromosome, two chromo- 

 somes, etc. ; 



(ii) in the disproportion of the excessive fraction to the rest, the 

 proportions being 3 to 2 (trisomic diploid) and 4 to 2 or 2 to i 

 (tetrasomic diploid and disomic haploid) . 



They also differ at different stages of the life cycle owing to 

 differences in the stringency of conditions of life. 



Thus the observations on fertility of numerically abnormal 

 zygotes may be used to measure elimination on three scales. Taking 



