The title of Raphaela Vogel’s exhibition “Gregor’s Loch” recalled many Gregors, among them Pope Gregory I, the gallerist Gregor Staiger, and Kafka’s Gregor Samsa. Loch, German for hole, could refer to a lair or a hideaway, which in this case might have been the gallery or perhaps an orifice, Gregor’s hole. It was tempting to see the title as intended to needle, to get at Mr. Staiger, who is known for his genial, imperturbable, lightly self-deprecating distance. You have to admire Vogel’s consistency: She never smooths over the awkward question of the artist’s relationship to a host institution.