QUIN1, in his study of the rumen micro-organisms occurring in sheep fed exclusively on lucerne hay, noted the appearance of large numbers of ovoid, clear cellular organisms with an average size of 8 µ × 4 µ. He showed that rumen fluid rich in these organisms rapidly fermented glucose with the evolution of gas, and that under these conditions the organism stained mahogany brown on the addition of aqueous iodine solution. He did not state whether these organisms were motile, nor did he record any attempts at isolation by cultural methods. On the basis of their apparent reproduction by binary fission and their fermentative powers, Quin considered that these organisms were a type of false yeast, and accordingly named them ‘Schizo-saccharomyces ovis'.