Is a bequest valid for property that cannot be immediately delivered?

Primary text

A bequest is valid concerning property that the testator cannot deliver immediately, such as an escaped slave, a stray camel, a bird in the air, or fish in the water. This validity is established because a bequest is analogous to inheritance, and these items can be inherited. If the executor gains control over the property after the testator's death, the beneficiary receives it, provided it does not exceed the one-third limit. The executor has the right to strive for its acquisition.