Chamber for critical-point drying of nematodes and other biological specimens.

Processing nematodes for scanning electron microscopy requires transfer of specimens through a series of fixatives and dehydrat ion fluids (1, 2). Preferably, all steps of fixation, dehydration, and drying are performed in the same vessel to avoid repeated handling of specimens. De Grisse (2) described small chambers made of nylon mesh and glass tubing for this purpose, and Marchant (3) constructed a similar device from small polypropylene vials and Millipore R filters. In our experience, the joints between chamber walls and screens m the first design (2) were not always tight enough. Rostgaard and Christensen (4) stated stringent requirements for such a chamber and made one from brass and a luminum stock. Its construction, however, involved extensive precision machine work. This paper describes a simpler, larger variant of tile same basic design which is fabricated by modification of commonly available hardware. Threaded components allow a tight fit between screens and chamber walls, and minimize the chances of losing small specimens. T h e basic material used to construct this uni t was a standard brass compression union for 9.5-ram (3/8 inch) flexible copper tubing (Coronet Part Manufactur ing Co., 883 Elton St., Brooklyn, N.Y. 11208). Half of the threaded portions on each end of the middle piece of the fitting were cut off. T h e