The author would like to extend his thanks and appreciation to several individuals whose efforts have made the publication of this work a reality. Chester T. Roskey, Framingham State College, Framingham, Massachusetts, and Thomas Settlemire, Bowdoin College, Brunswick, Maine, were instrumental in checking the manuscript for errors, suggesting changes and the like. Michael J. Timmons, Moraine Valley Community College, Palos Hills, Illinois, deserves special credit for developing the illustration program and for serving as an outstanding consultant. His efforts are especially appreciated. All photomicrographs were taken with the Bausch and Lomb Balplan microscope made available through the courtesy of William Westfall. Special thanks go to Cynthia Nickerson and Jeff Hotlmeier of D.C. Heath.  It is largely through their confidence and efforts that this work reached its present from.