Ivanov, Petr Pavlovich

Born Apr. 9 (21), 1878, in St. Petersburg; died Feb. 15, 1942, in Kostroma. Soviet embryolo-gist and professor (1918).

Ivanov graduated from the University of St. Petersburg in 1901. From 1912 until the end of his life he worked in the subdepartment of zoology of the medical department of the Institute of Psychoneurology (later the Second Leningrad Medical Institute); in 1924 he became subdepartment chairman. He was simultaneously chief of the embryology laboratory of Petrograd (Leningrad) University (from 1922) and of the laboratory of experimental embryology of the All-Union Institute of Experimental Medicine (from 1932). His principal works dealt with embryonic development and regeneration in annelids and arthropods. He developed a theory of larval segments (based on the distinctions, discovered by Ivanov, between primary, larval, and secondary, postlarval, segments) that established a general pattern of body segmentation in metameric animals.