RELIC COILING 33^ 



any definite structure has been observed in the chromosomes of 

 plants or animals at meiosis. 



Linear contraction of the chromosomes must depend on spiralisa- 

 tion. At the metaphase of mitosis it has been possible to see this 

 spiral in special preparations (Geitler, 1935 a ; Upcott, 1935 a). 

 Comparison with the succeeding stages leaves no doubt that the 

 same type of structure regularly obtains at mitosis. Moreover, it 



cT-^ ^f\^^ /-^'^'^ •vi"^%V^' 



R, P2 P3 P4 Ps ^ 



Fig. 6. — The uncoiling of relic spirals from telophase (T) to prophase 

 (P) and metaphase {M) in Fritillaria. Super-spirals appear 

 in Pg. X 1800. (D., 1935 a.) 



shows a mechanical relationship between succeeding divisions 

 (D., 1935 a). At the telophase a spiral becomes distinguishable, 

 corresponding to the supposed structure at metaphase. This is 

 the relic spiral. The same general structure is visible at the begin- 

 ning of the following prophase, except that the arrangement is 

 somewhat more contorted and the chromosomes have divided into 

 chromatids which are coiled round one another in a way that 

 presumably compensates for the relic spiral. As the chromatids 

 contract and, we must suppose, form internally the spiral which 

 they show at metaphase, they also gradually uncoil the relic spiral 



R.A. CYTOLOGY. 2 



