Cassianus, Scythian by race, ordained deacon by bishop John the Great, at Constantinople, and a presbyter at Marseilles, founded two monasteries, that is to say one for men and one for women, which are still standing. He wrote from experience, and in forcible language, or to speak more clearly, with meaning back of his words, and action back of his talk. He covered the whole field of practical directions, for monks of all sorts, in the following works: On dress, also On the canon of prayers, and the Usage in the saying of Psalms, (for these in the Egyptian monasteries, are said day and night), three books.
One of Institutes, eight books On the origin, nature and remedies for the eight principal sins, a book on each sin. He also compiled Conferences with the Egyptian fathers, as follows: On the aim of a monk and his creed, On discretion, On three vocations to the service of God, On the warfare of the flesh against the spirit and the spirit against the flesh, On the nature of all sins, On the slaughter of the saints, On fickleness of mind, On principalities, On the nature of prayer, On the duration of prayer, On perfection, On chastity, On the protection of God, On the knowledge of spiritual things, On the Divine graces, On friendship, On whether to define or not to define, On three ancient kinds of monks and a fourth recently arisen, On the object of cenobites and hermits, On true satisfaction in repentance, On the remission of the Quinquagesimal fast, On nocturnal illusions, On the saying of the apostles, “For the good which I would do, I do not, but the evil which I would not, that I do,” On mortification, and finally at the request of Leo the archdeacon, afterwards bishop of Rome, he wrote seven books against Nestorius, On the incarnation of the Lord, and writing this, made an end, both of writing and living, at Marseilles, in the reign of Theodosius and Valentinianus.
Source: Illustrious Men (Supplement to Jerome) (New Advent)