DILUTION MEDIUM AND SURVIVAL OF THE SPERMATOZOA OF ARBACIA PUNCTULATA. I. EFFECT OF THE MEDIUM ON FERTILIZING POWER

¹ Department of Zoology, University of Missouri, Columbia, Missouri

1. A factor is present in the seminal fluid of Arbacia punctulata which prolongs the fertilizing capacity of the sperm cells of the same species.

2. The factor, which is not found in the coelomic (perivisceral) fluid, is heat-sensitive, precipitated by saturation with ammonium sulfate, non-dialyzable, and surface-active on glass. Since micro-Kjeldahl analysis of the seminal fluid gives positive results corresponding to 2.5 mg. protein per cc. of seminal fluid, it is tentatively suggested that the factor is protein.

3. Seminal fluid has a pH range of 7.6 to 7.9, its osmotic pressure is approximately 10 per cent lower than sea water, and its content of reducing sugar is negligible.

4. In equivalent concentration and immediately after suspension the fertilizing capacity of the individual spermatozoön is greater in seminal fluid than in sea water.

5. Seminal fluid does not contain antifertilizin since it does not neutralize the agglutinating action of egg-water; indeed, this action is intensified.

6. A tentative mechanism, based on the adsorption of a fertilizing substance and its removal from the surface of the sperm cell, is suggested to explain the experimental results. It is proposed that the seminal fluid factor is this fertilizing substance before adsorption and while on the surface of the sperm; it becomes changed upon removal from the sperm surface.

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