Improved Method of Phage Assay by a Plaque Count Method on Microscope Slides in Trays.

' Supported by grant no. E-2379 from the National Institutes of Health, U. S. Public Health Service. Since then, the Jones-Krueger method has been further simplified by placing a large number of slides on moistened blotters in flat trays which are then covered with glass sheets to retain moisture. Using trays 33.7 cm long, 23.5 cm wide, 1.3 cm high, the authors have routinely placed 32 slides per tray and have incubated trays in stacks of 6. This technique has proved much faster and more economical of medium and space than the Gratia technique. The method works well with the P14 and Pi, 758 NOTES [VOL. 79