The reproductive organs of the male giraffe differ little in morphology and histology from those of other ungulates. There is some indication that gonadal hypertrophy occurs in late fetal life. Spermatogenesis begins at 3-4years of age and coincides with a rapid increase of testicular weight and seminiferous tubule diameter. In the fetal testis the main hormone is androstenedione (2.73 microgram/g) but in adult testes testosterone is predominant (<10.08 microgram/g) and delta' testosterone may also be present.
