IN 1912, I published (Ber. d. bot. Ges.) a preliminary note on the constant symbiosis of Aphides with Azotobacter. The entomologist, Prof. K. Aulc, of Brno, had previously (1910) found that the hitherto mysterious function of an organ in aphides and similar insects, called the pseudovitellus, was a seat of symbiotic organisms. I succeeded in isolating and identifying them as belonging to the genus Azotobacter, and in 1916 published the results of my studies in the Prague Zemedelsky Archiv.