Meiosis and some aspects of cytological mechanisms of chromosomal sex determination in nematode species.

Meiotic division in Toxascaris leonina, Baylisascaris transfuga, Hexametra sp., Toxocara canis, T. cati, Heterakis gallinarum and Physaloptera clausa of the class Nematoda were studied. Chromosomal sex determination type in different taxa is described. The XX-XO type of sex determination predominates in the species examined. A Y chromosome occurs only in B. transfuga. A correlation between the number and length of sex chromosomes and autosomes in the different taxa was established.