Preparation of embryonic tissues for SEM.

Examination of the SEM literature regarding embryonic stages of a variety of animal species reveals that similar results may be obtained using a range of preparative techniques, but that images of significantly different quality may also be obtained by different investigators studying similar tissues processed by presumably identical methods. This paper provides a discussion of basic procedures which may be used to obtain "good" quality images of embryonic stages of a variety of representative species including insect, marine invertebrate, amphibian, avian and mammalian forms commonly used in developmental biology. It is hoped that such information will serve as an initial starting point for those with little or no previous experience in preparing embryonic specimens for SEM examination. In addition to comments regarding fixation, dehydration, drying and preparation of a conductive surface, representative procedures for procuring, handling and removal of extraembryonic layers are also mentioned. Some of the more common types of artifacts are also considered in an attempt to aid in interpretation of micrographs.