The Osmotic Properties of the Eggs of the Trout (Salmo Fario)

Abstract

1. The normal healthy eggs of the trout are impermeable both to water and to intracellular electrolytes. The barrier to diffusion of both water and salts lies in the vitelline membrane, whose static properties maintain the normal hypertonicity of the yolk without expenditure of energy. 2. When eggs are exposed to conditions which destroy the normal impermeability of the vitelline membrane, exosmosis occurs suddenly at the end of a latent period, and once it has begun exosmosis is usually rapidly completed. Exosmosis is a sign of an unhealthy cell. 3. The osmotic stability of the vitelline membrane varies with four factors: (a) the age of the eggs, (b) the degree of mechanical disturbance caused by the environment, (c) the presence or absence of calciuim in the environment, (d) the nature and concentration of the exosmotic reagent used. 4. Loss of the impermeable properties of the vitelline membrane is accompanied by a drastic change in the distribution of the material of the membrane and in the organisation of the egg cell.