Then in 1867 when offered a professorship by the University of Würzburg he accepted, expressing deep regret at leaving Zurich but finally finding he could no longer resist his wish to return to his native Germany.
Pagkatapos ay sa 1867 kapag inaalok ng isang pagkapropesor ng University of Würzburg siya tinanggap, expressing malalim panghihinayang at umaalis Zurich ngunit paghahanap sa wakas siya ay hindi na labanan ang kanyang nais mong bumalik sa kanyang katutubong Germany.