484 



CELL MECHANICS 



would slip round one another freely as they shortened and straight- 

 ened so as to lie parallel at metaphase. These attractions will be 

 dealt with later. 



Fourthly, the separation of daughter ring-chromosomes shows 

 that a cleavage surface is predetermined within the coiled chromosome 

 in the resting stage along a spiral compensating for the relic spiral. 



Relation- 

 ship 



Struc- 

 ture 



Type in order of increasing 

 diameter 



Duration 



Mitosis 

 M-A 



Meiosis 

 M-A T 





V) 



3 O C 



•a c o 



C TJ- Is 



C vO 



o . 



CO ^-' 



^^ 





S 

 o 



o 



A — Original spirals (in metaphase of the 

 mitosis of origin) — 



1 Molecular spiral (R) 



2 Minor spiral (L) 



3 Major spiral (L) 



B — Derived or transferred spirals — 



4 Super-spiral (by transfer from 2 and 3 

 (L) ) 



5 Relic spiral from 2 or 3 (L) 



6 Inter-chromatid spiral (R) (opposite 



to II) 



7 Inter-chromosome spiral (L) 



X X X X X 



X X X X -* 

 > XXX 



X X X X X 



X X X X -». 

 >. XXX 



X -V X X X 



X -+ X X X 



Fig. 135. — Relationships of different kinds of spiral structure, in 

 space, time and (provisionally) in direction. (D., 1935 a.) 



These conclusions, in answering some of the questions of internal 

 mechanics, raise several new questions : — 



(i) The internal spirals are evidently consistent for considerable 

 parts of chromosomes. Are they consistent for whole chromosomes 

 or for whole arms ? 



(ii) If they are, and a molecular spiral determines coiling, what 

 is it that co-ordinates the molecular spiral ? 



(iii) Further, a molecular spiral must be supposed also to deter- 

 mine the relational coiling of chromosomes at pachytene by the 



