apam-of water; viryasya-of the semen; sargasya-of the generative; parjanyasya-of rains; praja-pateh-of the creator; pumsah-of the Lord; sisnah-the genitals; upasthah tu-the place where the genitals are situated; prajati-due to begetting; ananda-pleasure; nirvrtih-cause.