1. The spermatophoric reaction in the giant octopus requires 1-2 h, and during that time the large mass of spermatozoa contained in the proximal (male-oriented) portion of the spermatophore, is propelled over a metre-long distance to the distal (female-oriented) end.

2. Osmotic pressure provides the main mechanism for the spermatophoric reaction; and the influx of sea water, as a result of which the intraspermatophoric fluid space increases fivefold, provides the main force for driving the spermatozoa from the proximal to the distal end of the spermatophore.

3. The outer tunic of the spermatophore acts as a semipermeable membrane, permeable to sea water but not to macromolecular substances. Its strength is adequate to resist inside pressure 400 cm water in excess of the external environment.

4. In the normal course of spermatophoric reaction intraspermatophoric hydrostatic pressure increases from about 140 cm water at the onset of the reaction to about 330 cm H2O at the moment when the cap of the spermatophore ruptures and the ejaculatory apparatus is extruded; the rate at which pressure increases during this phase of the reaction is about 8 cm H2O/min.

5. Immediately after the extrusion of the ejaculatory apparatus the pressure falls precipitously. It then increases once more, but very slowly, reaching 45-95 cm H2O before the ejaculatory apparatus evaginates. It declines once more during the final stage of the evagination process. At the end of the spermatophoric reaction the transmural pressure is only about 9 cm H2O in the spermatophoric bladder but approximately 4 times higher in the proximal portion of the spermatophore.

6. In spite of the increase in the concentration of sodium and chloride ions in the intraspermatophoric fluid, the osmolality of that fluid remains largely unaltered throughout the whole spermatophoric reaction, but always at a level distinctly higher than the surrounding water (by about 30 mOsm/kg water).

7. Large-molecular glycoproteins in the spermatophoric plasma are probably undergoing enzymic breakdown by glycosidases during the spermatophoric reaction, as a result of which some carbohydrate, aminosugar and other nitrogenous organic material pass from the interior to the exterior of the spermatophore.

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