Environmental Scanning Electron Microscopy has opened up the potential to study biological events in their native occurence. While still in the early stages of exploration, the ability to view samples in their native state with the resolution provided by scanning electron microscopy is highly desirable and will provide insights in dynamic processes which previously had only been possible by interpretation with indirect methods or by static images obtained with transmission electron microscopy.

In preliminary experiments to explore the potential of studying native events with the ESEM we have investigated sea urchin embryos after deciliation with chloral hydrate. The Philips XL-30 ESEM instrument was used to obtain images of lightly fixed (0.1% glutaraldehyde in sea water), lightly coated embryos that had been treated as follows. Chloral hydrate was added at a concentration of 0.1% to blastulae of Lytechinus pictus at 24 hours after fertilization. Observation with light microscopy indicates that cilia become gradually shed into the sea water within 10 to 20 hours after chloral hydrate application.