And God blessed them, saying,
Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth.
All Commentaries on Genesis 1:22 Go To Genesis 1
Ambrose of Milan
What pure and untarnished generations follow without intermingling one after another, so that a thymallus produces a thymallus; a seawolf, a seawolf. The seascorpion, too, preserves unstained its marriage bed…. Fish, therefore, know nothing of union with alien species. They do not have unnatural betrothals such as are designedly brought about between animals of two different species as, for instance, the donkey and the mare, or again the female donkey and the horse, both being examples of unnatural union. Certainly there are cases in which nature suffers more in the nature of defilement rather than that of injury to the individual. Man as an abettor of hybrid barrenness is responsible for this. He considers a mongrel animal more valuable than one of a genuine species. You mix together alien species and you mingle diverse seeds. .