The chromosomes are arranged telosynaptically in O. muricata. At the end of prophase, all of the 14 haploid chromosomes are arranged end to end in 1 series, forming a closed circle. This circle remains intact throughout the heterotypic metaphase, adjacent chromosomes being pulled toward opposite poles, thus giving to the circle a regular zigzag appearance. The circle becomes broken in the heterotypic anaphase by the separation of adjacent chromosomes to opposite poles. Irregularities occur in the zigzag arrangement in approximately 20% of the cells. The chromosomes are considered to have definite positions within the circle, and, with adjacent chromosomes going to opposite poles, they are thus distributed in anaphase in such a way that the same chromosome complexes are formed at the poles in all normal cells. There is consequently but 1 linkage group in this species. Irregularities in the zigzag arrangement doubtless lead to abnormal distribution of the chromosomes, which, in many cases, may afford a sufficient cytological basis for the phenomenon of crossing over.