**CROTUS (Rubianus), Johann.** German humanist, b. at Dornheim (Arnstadt) in Thuringia, 1480; d. at Halle in 1539. His real name was *Jäger*, which is often found translated into Latin as *Vetator*. He studied at the University of Erfurt, where in 1500 he obtained the bachelor’s degree.
Having moved to Fulda (1510), he there met Conrad Mut(h) (*Mutianus*) and Ulrich von Hutten, with whom he composed the *Epistolae obscurorum virorum* (1515). From 1517 to 1520 he sojourned in Rome and Bologna. On his return to Germany he was named rector of the University of Erfurt, and in that capacity warmly welcomed Luther on his way to the Diet of Worms (1521), extolling him in a solemn address as the one «qui primus post tot saecula ausus fuit gladio sacrae scripturae romanam licentiam jugulare». But when later he perceived that Luther was not working for the Church’s good but for its destruction, he openly opposed the reform movement. Luther therefore heaped abuse upon him, calling him an Epicurean and Dr. Kröte (= “toad”).
In 1530 he entered the service of the Elector-Archbishop Albert of Mainz, and the following year published an apology to defend him against the attacks of the Lutheran Alexis Crosner: *Apologia, qua respondent temeritati calumniatorum non verentium confictis criminibus in populare odium protrahere Reverendissimum in Christo patrem et dominum Albertum… a Joanne Croto Rubeano privatim ad quendam amicum conscripta* (Halle 1531). The Archbishop of Mainz, in gratitude, appointed him canon of Halle.