And God created great sea creatures, and every living thing that moves, which the waters brought forth abundantly, after their kind, and every winged fowl after its kind: and God saw that it was good.
All Commentaries on Genesis 1:21 Go To Genesis 1
Basil the Great
The nature of existing objects, set in motion by one command, passes through creation without change, by generation and destruction, preserving the succession of the kinds through resemblance until it reaches the very end. It begets a horse as the successor of a horse, a lion of a lion and an eagle of an eagle. It continues to preserve each of the animals by uninterrupted successions until the consummation of the universe. No length of time causes the specific characteristics of the animals to be corrupted or extinct, but, as if established just recently, nature, ever fresh, moves along with time.