Arcesilaus, a native of Lampsacus, whom he mentioned in his will; a distinguished man who is generally known as “ the physicist,’ because more than anyone else he devoted himself to the most careful ‘study of nature. Moreover, he taught Ptolemy Philadelphus and received, it is said, 80 talents from him. According to Apollodorus in his Chronology he became head of the school in the 123rd Olympiad,* and continued to preside over it for eighteen years. There are extant of his works : Of Kingship, three books. Of Justice, three books. Of the Good, three books. Of the Gods, three books. On First Principles, three books. On Various Modes of Life. Of Happiness. On the Philosopher-King. Of Courage. On the Void. On the Heaven. On the Wind. Of Human Nature. On the Breeding of Animals. Of Mixture. Of Sleep. Of Dreams. Of Vision. Of Sensation. Of Pleasure. On Colours. Of Diseases.