This text is missing some spaces, please add them: ThemathematicalseminarinBerlinhadbeenjointlyfoundedin1861byKummerandWeierstrassand,whenKummerretiredin1883,Kroneckerbecameacodirectoroftheseminar.
The mathematical seminar in Berlin had been jointly founded in 1861 by Kummer and Weierstrass and, when Kummer retired in 1883, Kronecker became a codirector of the seminar.