Cal. CORP § 412

Every transferee of partly paid shares who acquired them under a certificate or initial transaction statement showing the fact of part payment, and every transferee of such shares (other than a transferee who derives title through a holder in good faith without knowledge and who is not a party to any fraud affecting the issue of such shares) who acquired them with actual knowledge that the full agreed consideration had not been paid to the extent stated on the certificate or initial transaction statement, is personally liable to the corporation for installments of the amount unpaid becoming due until the shares are transferred to one who becomes liable therefor; provided that the transferor shall remain personally liable if so provided on the certificate, initial transaction statement, or written statement, or agreed upon in writing.