120 The Structure of Protoplasm 



ism of "condensation" or better, of "packing" (Darlington) . Maxi- 

 mum spiralization occurs at metaphase or early anaphase in plants 

 with large chromosomes (and probably in almost all organisms) but 

 at the end of anaphase in some protozoa (Belar, 1926, Bauer, 

 1938) . For the purpose of analysis it is necessary to consider the 

 many different forms that coiling may take or stages that may occur 

 in the process. The chromonema within each chromatid of a mitotic 

 chromosome forms a helix which is best termed a standard coil 

 (Nebel, 1939) . The two chromatids are twisted about each other 

 like the two strands of electric flex, i. e., they are extended coils 

 turning in the same direction. This is termed relational coiling 

 (Darlington, 1935b) . In the prophase of mitosis, especially in the 

 first microspore division, the chromonemata are in loose spirals 

 which Darlington termed relic coils. They have now definitely 

 been shown, in pollen grain divisions, to be the residuum of the coils 

 of the previous division, as his term implies (Sparrow, Huskins, and 

 Wilson, 1941) . 



At the metaphase and anaphase of meiosis, there is typically a 

 coil of much larger diameter. Fujii, in 1926, first described the 

 chromonema forming this coil as being itself a small-gyred spiral. 

 These two helices are now generally termed the major and minor 

 coils (Huskins and Smith, 1935) . In some organisms, e. g., Trillium, 

 the major coil persists relatively unchanged through both divisions 

 of meiosis and appears as a large- gyred relic coil in the prophase of 

 the first pollen grain division. In others, e. g., Tradescantia, the major 

 coil disappears during meiotic interkinesis and a new smaller-gyred 

 spiral appears in the second division. 



In my opinion much confusion has resulted from the use of terms 

 with implications beyond those warranted by the existing data and 

 from failure to keep theory sharply differentiated from observation. 

 For instance, the major and minor coil were originally termed pri- 

 mary and secondary, and the terms were then interchanged as 

 evidence accumulated on their relationship. The small-gyred coil 

 of the second meiotic division in Tradescantia and that of somatic 

 cells have often been called minor coils, thus implying a relationship 

 with the minor coil of the first division of meiosis which is not yet 

 established. The frankly deductive hypothesis of coiling presented 

 by Darlington (1935b) relates all the different coils, and traces 

 them back to an assumed molecular spiral unitarily controlled 

 from the centromere or kinetochore. Certain of Darlington's fol- 

 lowers took the molecular spiral as a datum and when they found 



