Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 3


मासेन तु शिरो द्वाभ्यां बाह्वङ्‌घ्र्याद्यङ्गविग्रह: ।नखलोमास्थिचर्माणि लिङ्गच्छिद्रोद्भवस्त्रिभि: ॥ ३ ॥


māsena tu śiro dvābhyāṁbāhv-aṅghry-ādy-aṅga-vigrahaḥnakha-lomāsthi-carmāṇiliṅga-cchidrodbhavas tribhiḥ


In the course of a month, a head is formed, and at the end of two months the hands, feet and other limbs take shape. By the end of three months, the nails, fingers, toes, body hair, bones and skin appear, as do the organ of generation and the other apertures in the body, namely the eyes, nostrils, ears, mouth and anus.