Cytology is the subject that is dealt with in this autoinstructional program. The process to be understood by secondary school students who are taking biology is mitosis. The material is presented to be adequate for achievers at the middle level. Knowledge of the structure of the DNA molecule and of the parts of the cell are considered as prerequisites for this lesson. Three behavioral objectives are suggested. Equipment and materials needed are itemized. Approximately 15 minutes is needed. A vocabulary sheet, a student script and a suggested method of evaluation are included in this packet. (EB)