Particles averaging 3 to 4 µ in diameter, which are called chromospheres and fill the immature meiosporangia of the watermold Allomyces, were isolated and analyzed. The preparations were obtained by repeated centrifugations or by passage of the homogenate into a column of sand saturated with oleic acid, followed by selective elution of the chromospheres with alternate layers of oleic acid and an aqueous solution.

The chromospheres contain approximately 12 per cent RNA, no DNA, and 60 per cent protein. It was concluded that they are pure or nearly pure ribonucleoprotein. Analysis of meiosporangia with chromospheres and after the chromospheres have disappeared showed no significant change in RNA or free amino acids. It was concluded that chromosphere disappearance is a fragmentation into small granules.

The relation of chromospheres to postmeiotic chromospheres and nuclear caps is discussed. Speculation as to the function of these bodies is presented.

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