Abstract
The vitamin B_<12> content in earthworms was studied in association with conditions of the soil in which they lived. There were many Actinomycetes and earthworms in the soils containing much decomposable organic matters. The vitamin B_<12>-forming Actinomycetes were found in the alimentary tract of earthworms as well as in the soils, and the number of the microbes in earthworms varied correspondingly with their number in soils. The vitamin B_<12> content of earthworms were influenced by these microbes in their alimentary tract.
