Outstanding vertebrate zoologist, acknowledged leader of Moscow school of mammalogy. Graduated from Moscow University in 1910, kept at Zoology Department and the Museum as an assistant of Kozhevnikov, his superviser. Read courses on zoogeography, mammal biology, ecology. Ranked professor of zoology at Pedagogical Institute in 1928, chief of Zoological Department of that institute since 1941, professor of zoology at the Moscow University. However, it was the Museum where his working cabinet was placed since late 1920s.Was first in Russia to study smaller mammals, and the first to understand need for the large samples for studying their taxonomy at species level. Participated in many expeditions which allowed him to gather quite significant private collection (now in the Museum). Published his first monograph on smaller mammals of Moscow Region in 1910. Main result of his research career became the multi-volumed “Mammals of Russia and adjacent territories” (unfortunately remained unfinished). Also published fundamental textbooks on mammal ecology, vertebrate zoology, etc.