I've posted a message twice to this list, and never seen it appear yet ... perhaps this one will go through ... ? -- Aaron J. Mackey, Ph.D. Dept. of Biology, Goddard 212 University of Pennsylvania email: amackey at pcbi.upenn.edu 415 S. University Avenue office: 215-898-1205 Philadelphia, PA 19104-6017 fax: 215-746-6697