Meiosis in Hansenula holstii and H. wingei.

Diploid isolates of Hansenula holstii Wick. and H. wingei Wick. usually produce two or three ascospores per ascus. An unusual nuclear event during meiosis might account for less than the expected number of four. When acridine orange or Feulgen staining was used, meiosis in both species followed the pattern established in higher plants and animals. Deoxyribonuclease treatment destroyed nuclear staining material. Six chromosomes were seen during prophase I. Three bivalents seen during metaphase I divided and moved to two poles with loss of distinct chromosomes for the remainder of meiosis. When only two or three spores were formed in an ascus, apparently normal nuclei, not enclosed in spore walls, were pushed against the ascus wall. The haploid (n) chromosome count in both H. holstii and H. wingei was shown to be three.