Complex sentence: He also made a collection of over 5,000 pieces of Japanese pottery, and became Keeper of Pottery at the Museum of Fine Arts in Boston in 1890, which now contains his pottery collection, the Morse collection.
Split into simpler sentences: He also made a collection of over 5,000 pieces of Japanese pottery. Morse became Keeper of Pottery at the Museum of Fine Arts in Boston in 1890, which now contains his pottery collection, the Morse collection.