Days 5–6: fishes, birds, land animals, and humankind
XVIII. The work of the fifth day is the production of fishes and birds for the adornment of the waters and the air. For just as on the fourth day stars are made for the adornment of heaven, so on the fifth fishes and birds for the adornment of the waters, and on the sixth walking things and reptiles for the adornment of the earth. Therefore, as if by critical correspondence, the first answers the fourth, the second the fifth, and the third the sixth. God said: Let the waters bring forth the creeping thing of living soul and the flying thing upon the earth. This precept is the institution of nature, completed by power, wisdom, and love, and is called the art of God implanted in things, leading them to their ends.
XIX. The work of the sixth day is the production of all the living things of the earth of three kinds. XX. And it is of brutes or of those endowed with reason. Concerning the creation of brutes Moses in Genesis 1:24–25, teaching, constitutes three genera of them — namely some cattle and tame, reptiles, others wild and sylvan — of whose nature and use philosophers treat more fully and more subtly in Physics. These were fittingly produced on the sixth day from the earth, which answers the third; and after the less perfect species the more perfect are made, and finally humankind, the most perfect of all.
Latin
XVIII. Opus quinti diei est productio piscium et avium ad ornatum aquarum et aeris. Sicut enim quarto die fiunt stellae ad ornatum caeli, ita in quinto pisces et aves ad ornatum aquarum; in sexto vero gressibilia et reptilia ad ornatum terrae. Quapropter quasi critice respondet primus quarto, secundus quinto, tertius sexto. Dixit Deus: Producant aquae reptile animae viventis et volatile super terram. Hoc praeceptum est naturae institutio quae integratur a potestate, sapientia et amore, et dicitur ars Dei rebus indita ducens eas ad suos fines. XIX. Opus sexti diei est productio omnium animantium terrae trium. XX. Estque brutorum aut ratione praeditorum. De brutorum creatione Moses Gen. I.24–25 docens tria eorum genera constituit — alia nempe pecuina et mansueta, reptilia, alia fera et silvestria — de quorum natura et usu philosophi plenius et subtilius exequuntur in Physicis. Convenienter autem haec sunt producta in die sexto e terra, qui respondet tertio, et post imperfectiores species fiunt perfectiores, et tandem homo omnium perfectissimus.