The primary spermatocytes of homozygous males have no Y chromosomal lampbrush loops at 26oC. At 18oC, the morphology of all the Y chromosomal lampbrush loops is abnormal. The nuclear envelope of primary spermatocytes can undergo the morphogenetic movements characteristic for meiotic prophase. Meiotic divisions do not occur in homozygous males, while female meiosis and the gonial divisions are normal.