There was practically no passage of Ca or sulphate ions while ammonia, dichromate, chloride, or bromide ions readily permeated the corpuscle. The corpuscles were practically impermeable to eosin, erythrosin, phenol red, and acriflavine, but were fairly permeable to acid fuchsin, toluidine blue, and Bismarck brown. Organic compounds such as urea and glucose permeated the corpuscles. By means of raw egg-white, it was shown that protein as well as the lipid envelope exerted a selective permeability to salts.