The tetrahymenal MI of the crescent changes from spherical (stage I) to ellipsoid in early stage II after the MI frees itself from its home pocket in the edge of its MA. In late stage 2, the MI becomes spindle-shaped. Later in stage III, it assumes the form of a torch. During stages I-III, the distribution of chromatin in the crescent is polarized. There is a dense mass of chromatin threads near one end of the elongating MI.

In stage III nuclei, the region on the side of the dense chromatin is elongated and narrowed into a neck with a thickening like a head at the end. Most of the central body contains less dense parallel chromatin threads. These threads are somewhat like the minichromosomes of the MA. This stretching of the MI is followed by further, extreme elongation to form the crescent as in stage IV.

MI elongation is promoted by intranuclear microtubules. During stages V and VI, the MI shortens again, which finally leads to the formation of 5 metacentric chromosomes at what might be understood as diakinesis of metaphase I. Remember that when these 5 chromosomes start to condense, they stop transmitting. There is certainly no need to copy Darlington stages !