Light micrograph (LM) of a section of testis of a monkey. The testicle or testis is the male gonad in animals. Like the ovaries to which they are homologous, the testicles (testes) are components of both the reproductive system and the endocrine system. The primary functions of the testes are to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone. Magnification: 300x at 35mm.