Abstract
1. The seminal plasma of Balanus balanus has been analysed for a number of organic substances including total nitrogen, protein, urea, protein-bound hexose, hexosamine, fucose, ‘sialic acid’, glycogen, and RNA. The material was separated into soluble and insoluble fractions by precipitation with ethanol. 2. A large part of the ethanol-soluble material is inorganic salts and glycine; it contains a small quantity of protein-like material which on hydrolysis yields largely glycine and glutamic acid. 3. The alcohol-precipitated material contains protein, protein-bound hexose, hexosamine, lipids, and RNA. Glycogen, fucose, and ‘sialic acid’ are absent. 4. It is suggested that the plasma contains glycoproteins of a mucoid nature: the absence of both fucose and ‘sialic acid’ suggests that the mucoid may be of a relatively simple character. 5. Attention is drawn to the similarity of this seminal plasma, which is produced in the absence of accessory male organs, to that of higher animals.