TYPES OF COILING 491 



change being in opposite directions or in different degrees in the 

 two cases (D. 1935 c). 



Answering these questions of causation must needs wait upon a 

 related study of all the spiral formations, internal and relational, 

 in the same pair of chromosomes at different stages of the nuclear 

 cycle. The direction of relational coiling of chromatids at meiosis 

 may be recognised with difficulty in Orthoptera (D., 1936 h) or in 

 anomalous nuclei in plants (D., 1936 e). The direction of the minor 

 spiral has been said to be opposite to that of the major spiral (Iwata, 

 1935)- These structures, however, are on the limit of visibility, 

 hence it is necessary to test their observation by the most rigorous 

 inferences at every step. We must not suppose, as some authors 

 do, that the present apparent indeterminacy is final and irremediable. 

 Meanwhile, it is important to recognise the contradictions between 

 our present observations of relational and internal coiling in order 

 to find out their cause. These contradictions do not affect our 

 consideration of external mechanics. 



Table 71 



Observations of Chromosome Coiling 



1. Mitosis. 



(a) Metaphase, Internal Spirals. 

 Allium, Gasteria. Geitler, 1935 b, c. 

 Tulipa. Upcott, 1935. 



(b) Telophase and Prophase, Relic Spirals. 

 Stenobothrus. Janssens, 1924. 

 Tettigonia. de Winiwarter, 1931. 



Tradescantia. Kaufmann, 1926 ; Kuwada and Nakamura, 1934 ^» 



Plate XIII. 

 Tulipa. Upcott, 1936 b. 

 Galtonia. Newton, 1924. 

 Fritillaria. D., 1935. 



(c) Prophase and Metaphase, Relational Chromatid Spirals. 

 Many plant species. Lewitsky, 1931 (presumed). 

 Fritillaria, Puschkinia. D., 1935 a, 1936 c and d. 

 Locusta (diplochromosomes) . White, 1935. 



2. Meiosis (ist Division). 



{a) Metaphase : Major Spirals. Major and Minor Spirals. 



Tradescantia . Baranetsky, 1880. Fujii, 1926 cit. Kuwada. 



Sakamura, 1927. Kuwada and Nakamura, 1933. 

 Nebel, 1932 b. Sax and Humphrey, i934- 



Kato, 1935- 

 La Cour, 1935. 



