THE EMBRYOLOGY OF LYTTA VIRIDANA LE CONTE (COLEOPTERA: MELOIDAE): II. THE STRUCTURE OF THE VITELLINE MEMBRANE

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Abstract
This paper deals with the structure of the vitelline membrane of Lytta viridana as seen through the light microscope and the electron microscope. Through the light microscope, the vitelline membrane of a freshly laid egg appears to be porous. This condition persists for 15–30 min. During this time the pores become progressively smaller until the membrane becomes solid and continuous. The electron microscope reveals that the vitelline membrane of the freshly laid egg is actually composed of a three-dimensional membranous system which condenses into a homogeneous membrane after 15–30 min. The apparent porosity of the membrane as seen through the light microscope is interpreted in terms of its fine structure, and the belief is expressed that solidification of the membranous system is initiated by sperm penetration.