In the course of time, a certain transaction occurred, by means of which Ptolemy involved himself in serious difficulty with Philip, though by the same means he made Alexander very strongly his friend. There was a province of the Persian empire called Caria, situated in the southwestern part of Asia Minor. The governor of this province had offered his daughter to Philip as the wife of one of his sons named Aridæus, the half brother of Alexander. Alexander's mother, who was not the mother of Aridæus, was jealous of this proposed marriage. She thought that it was part of a scheme for bringing Aridæus forward into public notice, and finally making him the heir to Philip's throne; whereas she was very earnest that this splendid inheritance should be reserved for her own son. Accordingly, she proposed to Alexander that they should send a secret embassage to the Persian governor, and represent to him that it would be much better, both for him and for his daughter, that she should have Alexander instead of Aridæus for a husband, and induce him, if possible, to demand of Philip that he should make the change. Alexander entered readily into this scheme, and various courtiers, Ptolemy among the rest, undertook to aid him in the accomplishment of it. The embassy was sent. The governor of Caria was very much pleased with the change which they proposed to him. In fact, the whole plan seemed to be going on very successfully toward its accomplishment, when, by some means or other, Philip discovered the intrigue. He went immediately into Alexander's apartment, highly excited with resentment and anger. He had never intended to make Aridæus, whose birth on the mother's side was obscure and ignoble, the heir to his throne, and he reproached Alexander in the bitterest terms for being of so debased and degenerate a spirit as to desire to marry the daughter of a Persian governor; a man who was, in fact, the mere slave, as he said, of a barbarian king.