44 MITOSIS : THE CONSTANCY OF THE CHROMOSOMES 



Tradescantia that the polarised arrangement of the chromosomes 

 corresponded at prophase with that seen in the preceding telophase 

 {cf. Manton, 1935). Finally the recognition of a spiral arrangement 

 at prophase corresponding with that seen at telophase shows the 

 persistence of the chromosome structure during the resting stage 

 (Taylor, 1931 ; de Winiwarter, 1931). These observations show 



Fig. 9. — Mitotic metaphase : i. in Crepis capillaris {2n = 6) ; 

 2. in C. tectorum {2n = 8) ; 3. in the hybrid between them 

 {2n = 7). The chromosome types are marked with letters. 

 Note that the D chromosome of C. tectorum shows no trabant 

 in the hybrid. X 2300 (from Hollingshead, 1930 ; cf. Navashin, 

 1927). 



that the resting stage does not interfere with the structure and 

 relationship even of the constituent parts of chromosomes. The 

 chromosomes are not merely permanent but immobile. The 

 description as a " resting stage " is mechanically and morpho- 

 logically correct. 



(ii) Another kind of evidence consists in the demonstration of 

 the separate existence of the chromosomes during the resting stage. 

 This evidence is less decisive, because it may be held that such 



