Professor Bossert said he plans to work with a graduate student on the population biology of malaria, a subject he has never researched.

The Bosserts also plan to devote more time to their hobbies, which include restoring musical instruments, a model train set and traveling in their personal airplane.

The Bosserts said they announced their departure early in the year to allow a smooth transition for their successors.

A search for the Bosserts' successors has not yet begun.

"They will be very, very hard to replace," said Mellon Professor of the Humanities emeritus Zeph Stewart, who preceded the Bosserts as Lowell House master.

"I'm very sorry that their term as masters is coming to an end, but after 23 years, I can see why," he said