l62 



STRUCTURAL HYBRIDS 



polo- 



Phrynotettix niagnus * 

 Acridinni 



Circotettix verruculatus . 

 Mus musculus (mutant) 

 Lahidura bid ens 

 Mecostethus gracilis 

 Stevoboihriis lineatus 

 He me robins stigma 

 Stauroderus bicolor 

 Melanophts femur-rubrum 

 B. Plants. 



jEgilops ovata X Triticum 



niciim (4^) 

 yE". cylindrica X /E. trmm ialis (4-1 

 Boiigainvillcea glabra 

 Zebrina pendida {^x) 

 Crepis hybrids 

 Aloe purpurascens * 

 Triticum vulgare . 

 PcBonia officinalis * 

 Allium Cepa X A.fistulosum * 



2. Fragmentation Heterozygotes. 



Vicia sativa X V . amphicarpa 

 Crepis leontodontoides x C. 

 marschalli (4A'), etc. 



3. Interchange Heterozygotes 



CEnothera biennis . 

 Tradescantia virginiana . 

 Anthoxanthum odoratum 

 Orgyia thyellina X O. antiqua 



4. Complex and Sex Heterozygotes {v. Ch. IX) 



Wenrich, 191 6. 



Robertson, 191 5. 



Carothers, 1931 ; Helwig, 1929. 



Painter, 1927 (deficiency)- 



W. P. Morgan, 1928. 



McClung, 1928 b. 



Belar, 1929 a. 



Klingstedt, 1933. 



D., 1936 d. 



Hearne and Huskins, 1935. 



Kagawa, 1929. 



Kagawa, 1931. 



Cooper, 1 93 1. 



D., 1929 c. 



Babcock and J. Clausen, 1929. 



Belling, 1931. 



Huskins and Spier, 1934. 



Dark, 1936. 



Levan, 1936. 



Sveshnikova, 1929. 

 Avery, 1930 (Fig. 56). 



D., 1931 d. 

 D., 1929 c. 

 Kattermann, 1931. 

 Cretschmar, 1928. 



The differences between these chromosomes can be accounted for 

 by the assumption of simple structural changes in a way that will 

 explain their behaviour at meiosis. Translocation, for example, 

 affords a simple explanation where, as in Circotettix, there is a 

 difference in position of the spindle attachment without difference 

 of size. But it is probable, more especially in species hybrids, that 

 numerous structural differences distinguish the chromosomes. This 

 is clear in the hybrids of Lycia zonaria [n = 56) by L. hirtaria (« =14) 

 (Harrison and Doncaster, 1914), Lycia pomonaria (n = 51) by 

 L. hirtaria (n = 14) (Malan, 1918), and Orgyia thyellina (n = 11) by 

 0. antiqua (n = 14). In each cross the chromosomes of one species 

 are smaller and more numerous than those of the other. 

 Fragmentation or fusion is therefore to be inferred. But in the 



Having symmetrical lateral chiasmata. 



