MONTHLY SURVEY OF VITAMIN B12 CONCENTRATIONS IN SOME WATERS OF THE ENGLISH LAKE DISTRICT

The vitamin B12 activity for Euglena gracilis of water from nine lakes of the English Lake District was assayed at 15 consecutive monthly intervals. Filtration through glass‐fiber filters was used to differentiate between dissolved vitamin and that in gross particulate matter. The average vitamin B12 concentrations correlated with what has previously been described as the evolutionary series of the lakes: the “primitive” rocky lakes of low productivity are low in vitamin B12, the “evolved” silted lakes, richer in sediments, nutrients, and organisms have higher levels of the vitamin.