1. Science and Mathematics Division, Eastern Oklahoma State College, Idabel, Oklahoma 74745, U.S.A. (e-mail: ),
2. Department of Biology, Pennsylvania State University-Shenango Campus, 147 Shenango Avenue, Sharon, Pennsylvania 16146-1537, U.S.A. (e-mail: ), and
3. Life Sciences, Northwest Arkansas Community College, Bentonville, Arkansas, 72712, U.S.A. (e-mail: )