Abstract: Apparatus for permanently and protectively mounting "wet" thin sections of biological specimens on microscope slides, wherein each specimen is initially bathed in a low-volatile solvent containing a low concentration of first polymerizable material. Such solvent is allowed to evaporate, whereby the liquid polymerizable material permeates and protects the specimen. Following solvent evaporation, a second polymerizable material is layered over the specimen. Preferably, the first and second polymerizable materials comprise a mixture of low-volatility, low-viscosity, liquid acrylic reactomers and a U.V. light-sensitive catalyst system. A conventional cover slip or other planar transparent member can be positioned over the polymerizable materials, and the same are polymerized by exposure to U.V. radiation. The first and second now-polymerized materials encapsulate the specimen on the microscope slide, become integral and completely hardened and are fully devoid of any solvent.