In article <01bc7363$a8dacf40$5c2d6dc2 at the-ross-box>, Jonathan and Lise wrote: > Anybody know of an article or book on the subject? You could start by reading something of the works of Gregor Mendel and Charles Darwin. Roger - - - - - - - - - - - - - - - - - - - - - Roger Whitehead, 14 Amy Road, Oxted, Surrey RH8 0PX Tel: +44 (0)1883 713074; fax: +44 (0)1883 716793