All are studious.

S.Matthew, on the upper left as one stands with one's back to the Titian, has an open-air study, and he makes notes as he reads.

His eagle is in attendance.

S.Mark, with his lion at ease under his chair, has also his open-air desk, and as he reads he thinks.

S.
John is indoors, reading intently, with a box full of books to fall back on, and a little angel peeping at him from behind his chair.