Reliable Preparative Procedures for the Cytological Study of Yolk-Laden Insect Eggs and Embryos

Yolk-laden insect eggs and embryos are easy to fix and section by the following procedure: 1) Fix with non- or slightly coagulant solutions after opening the envelopes for large eggs, or after superficial fixation and removal of the vitelline membrane for small ones. 2) Carefully embed fixed and washed specimens in a thick agar gel. 3) Dehydrate trimmed agar blocks, first with 70% ethanol, then with 2-ethoxy-ethanol. 4) After optional immersion in butanol-1, embed in Steedman's “Ester wax 1960.” 5) Section, mount and stain like paraffin sections. Results are compared to the cryosertioning method recently described by Hartmann.