A slave's sexuality was closely controlled. Slaves had no right to legal marriage "(conubium)", though they could live together as husband and wife "(contubernales)". An owner usually restricted the heterosexual activities of his male slaves to females he also owned; any children born from these unions added to his wealth. Cato, at a time when Rome's large-scale slave economy was still in early development, thought it good practice to monitor his slaves' sex lives, and required male slaves to pay a fee for access to their female fellow slaves.