what is the difference between these: the donation by a spouse to the other spouse of his undivided interest in a thing forming part of the community transforms that interest into separate property of the donee. Unless otherwise provided in the act of donation, an equal interest of the donee is also transformed into separate property and the natural and civil fruits of the thing, and minerals produced from or attributed to the property given as well as bonuses, delay rentals, royalties, and shut-in payments arising from mineral leases, form part of the donee's separate property. and this: "The transfer by a spouse to the other spouse of a thing forming part of his separate property, with the stipulation that it shall be part of the community, transforms the thing into community property. As to both movables and immovables, a transfer by onerous title must be made in writing and a transfer by gratuitous title must be made by authentic act