Mr. Mahaffy in his preface to The Empire of the Ptolemies states among other problems raised by Ptolemaic history the following: ‘How far does the observation, that we only know of one crown-prince with a wife (Soter II.) account for the divorce of that wife after his accession, and for the other apparent heartlessnesses in Ptolemaic history? Is the hereditary title recognised in the princesses, which no doubt led to their marriages with their reigning brothers, a relic of Pharaonic ideas, or a mere imitation of the successful experiment of Philadelphus?’ This article is an attempt to show that the former hypothesis is the true one, and that the marriages of the Ptolemies were dictated by their policy of conciliation, and were based on deeply rooted native prejudices.