Career
In 1889 he earned his doctorate from the University of Kiel with a dissertation on the spinnerets of the orb-weaver spider. Afterwards he worked as an assistant to Karl Brandt (1854-1931) at the zoological institute in Kiel. As a young man he carried out studies of freshwater plankton in Holstein lakes (1890-1895).
In May- 1898 he obtained his habilitation at Kiel for zoology and comparative anatomy, and a few months later took part as a zoologist in the Deutschen Tiefsee-Expedition (German Deep Sea Expedition) aboard the steamship "Valdivia".
In 1906 he was appointed associate professor in Kiel, and in 1911 became a scientific officer in the Preußischen Akademie der Wissenschaften in Berlin. In this position he worked as a publisher of scientific journals in the field of zoology, which included editorship of Das Tierreich (The Animal Kingdom.
From 1927). In addition to his research involving the 1898-1899 Deutschen Tiefsee-Expedition, he was tasked with processing material taken from the Plankton-Expedition (1889) and the Deutschen Südpolar-Expedition (1901-1903).
In his investigations, Apstein distinguished himself in research of Thaliacea.