After his return he began to concentrate his studies on microscopic organisms, which until then had not been systematically studied.
After his return he began to concentrate his studies on microscopic organisms, which then were not much studied.
After his return he began to concentrate his studies on microscopic organisms, which then were not much studied.
Machen Sie den Satz einfacher: After his return he began to concentrate his studies on microscopic organisms, which until then had not been systematically studied. Ausgabe: