Călugăreanu was born in Pomârla, Botoșani County; his parents were the possibly illiterate peasants Constantin and Glicheria.
In 1902, he received a doctorate in natural sciences from the University of Paris, his thesis topic being research into hemolysis through experimental physiology and physical chemistry.
[2][3] While in this post, he expressed displeasure at the fact that Hungary's authorities had recently opened universities at Szeged and Debrecen near the Romanian border.
Among the phenomena he investigated were nerve compression, plasmolysis in cartilage cells, the electrical conductivity of plasma during coagulation, intestinal respiration in Misgurnus fossilis, respiration in certain gastropod genera (Limax, Helix, Planorbis, Lymnaea), functional particularities of the silk glands of the silkworm and the effect of light upon planarians.
He published his results in numerous books, studies and articles that appeared in scientific publications domestically and abroad.