The paired ‘H’-shaped testes ofPotamon koolooense show histomorphological changes during various stages of maturity. Seminiferous tubules show different stages of spermatogenesis. A few undifferentiated or resting spermatogonia supply a new crop of germ cells for the next breeding season. In a tubule the meiotic divisions occur more or less synchronously in all the primary or secondary spermatocytes. Sperm consists of a head and mitochondrial vesicle which encloses axial filament and distal centrosome. Spermatogenesis activity is seasonal. Spermatogenesis begins in January-February, progresses slowly through March, reaching its peak in April-May. However, all the tubules do not mature simultaneously. Spermiation occurs during May and June, the spermatogenesis ceases gradually, and by December the testes enter a brief period of rest.