Mo. Rev. Stat. § 474.463

An exchange of corporate stock, or of bonds, promissory notes or other securities, for other stock, bonds, promissory notes or securities of the same corporation or obligor or its successor does not adeem a specific legacy of the stock, bonds, promissory notes or securities, and the devisee is entitled to those received by the testator in exchange to the extent that they are part of his estate. A change, by a stock split or like device, in the proportional interest in a corporation represented by a share of its stock, entitles a devisee of a specified number of shares to so many shares as are needed to represent the same proportional interest in the corporation as the specified number represented when the will was executed, whether the devise is specific, general or demonstrative.