24. When goods are delivered to the buyer on approval or "on sale or return" or other similar terms, the property therein passes to the buyer-(a) when he signifies his approval or acceptance to the seller or does any other act adopting the transaction; (b) if he does not signify his approval or acceptance to the seller but retains the goods without giving notice of rejection, then, if a time has been fixed for the return of the goods, on the expiration of such time, and, if no time has been fixed, on the expiration of a reasonable time.