An analysis was made of the C-banded karyotype of Strophosoma capitatum (Deg.). The results indicate that the chromosome number is 2n=22 and n%=10+Xyp. The examined karyotype shows a pericentromeric position of constitutive heterochromatin in all autosomes. The shorter arm of the X chromosome is heterochromatic while the y chromosome is wholly euchromatic. Successive stages of spermatogenesis were analysed.