Bhashya
तस्मिन्नेतस्मिन्नग्नौ देवा रेतो जुह्वति ।तस्या आहुतेर्गर्भः सम्भवतीति ।एवं श्रद्धासोमवर्षान्नरेतोहवनपर्यायक्र-मेण आप एव गर्भीभूतास्ताः ।तत्र अपामाहुतिसमवायि-त्वात् प्राधान्यविवक्षा—आपः पञ्चम्यामाहुतौ पुरुषवचसोभवन्तीति ।न त्वाप एव केवलाः सोमादिकार्यमारभन्ते ।न च आपोऽत्रिवृत्कृताः सन्तीति ।त्रिवृत्कृतत्वेऽपि विशेष-संज्ञालाभो दृष्टः—पृथिवीयमिमा आपोऽयमग्निरित्यन्यतम-बाहुल्यनिमित्तः ।तस्मात्समुदितान्येव भूतान्यब्बाहुल्या-त्कर्मसमवायीनि सोमादिकार्यारम्भकाण्याप इत्युच्यन्ते ।दृश्यते च द्रवबाहुल्यं सोमवृष्ट्यन्नरेतोदेहेषु ।बहुद्रवं चशरीरं यद्यपि पार्थिवम् ।तत्र पञ्चम्यामाहुतौ हुतायां रेतो-रूपा आपो गर्भीभूताः ॥
In plain words
In that very fire the gods offer seed, and from that offering an embryo is born. Through the progression of faith, soma, rain, food, and seed-offering, it is the waters themselves that take the form of embryos. Because water is inherent in the offering, the scripture emphasizes its predominance by stating that waters take the form of a person in the fifth oblation. Yet this does not mean waters act alone or exist uncombined; rather, things are named after their predominant element, just as earth or fire are so designated. Thus, combined elements in which water predominates are simply called water. Fluidity is clearly observed in soma, rain, food, seed, and bodily forms—for the body, though earthy, is rich in fluid. Thus, when the fifth offering is made, the waters taking the form of seed become embryos.
Close to the Sanskrit
In that very fire the gods offer seed. From that oblation an embryo comes into being, thus. Thus, through the sequential order of faith, soma, rain, food, and seed-offering, the waters themselves have become embryos. There, because waters are inherent in the oblation, there is the desire to express predominance—'waters become designated as persons in the fifth oblation.' However, waters alone do not initiate effects like soma, nor are the waters here uncombined. Even in the state of combination, the acquisition of a specific designation is observed, as in 'this earth is this' and 'this fire is this,' based on the predominance of one or another. Therefore, combined elements themselves, due to the abundance of water, participating in the ritual and initiating effects like soma, are called 'waters.' And abundance of fluidity is seen in soma, rain, food, seed, and bodies; and the body, although earthy, is highly fluid. There, when the oblation is offered in the fifth, waters taking the form of seed have become embryos.