Original: In February 1907, while still a student, he was employed by the Department of Zoology at the British Museum (Natural History), where he spent most of his working life as Assistant Keeper of Mammals.
Simplified: In February 1907, when he was still a student, he was employed by the Department of Zoology at the British Museum (Natural History). He he spent most of his working life there as Assistant Keeper of Mammals.