The institute was housed in a former Benedictine monastery, and the first years, poverty reigned and the work was hard; additionally, Spreiter had become Amrhein's personal secretary.

[1] Spreiter, on his return to Europe, learned that he was appointed as apostolic vicar on 13 March 1906,[2] succeeding Bishop Spiss.

He was ordained in St. Ottilien on 1 May, and returned to Africa in 1906, now overseeing all missionary and educational activities in his vicariate: "Every year he undertook a pastoral journey through his mission territory.

"[1] When World War I broke out, all German missionary activities were forcibly halted, and Spreiter was under house arrest in Dar es Salaam until 1920, when he was made to return to Germany,[1] "resigning" his post in Zanzibar on 24 November 1920.

Spreiter showed him a bone fragment he had picked up in a village near the Mbalawala Plateau, and another fragment he had found in a village called Makangaga, west of Kilwa Kivinje, which proved that dinosaur bones could be found hundreds of miles from Tendaguru, the initial aim of their expedition.