Unlike multicellular contractile systems, the division mechanism may have no resting state. The contractile ring is exerting tension at the time it becomes ultrastructurally demonstrable, and it is gone when the division has been completed. Its very organization may be the consequence of local contractility. In this circumstance, formation and function may prove to be different phases of the same process and distinctions between them may simply make exposition more convenient.

The many changes in organization, structure, and behavior that immediately precede and accompany division have been carefully studied for clues about the mode of formation and function of the division mechanism, and the results of such studies form an important part of the body of information about cell division. Some of the phenomena that occur during the period of division activity were carefully described before their relation to the process was understood, apparently in the hope that, as the details were revealed, the connections would become clear. These expectations have not always been realized, and the significance of some of the most striking and best-studied events remains enigmatic.

Prefurrow Phenomena

Stiffness changes

The cyclical increase in resistance to deformation of the whole cell has previously been described and discussed.