Nematode worms are amongst the commonest and most widely distributed animals on Earth. Many species cause serious diseases of humans and livestock and as such are responsible for much economic loss in agriculture. However, almost all animals and plants are susceptible to attack by parasitic nematodes. Although they are probably best known as parasites, most nematodes are free-living and occur in enormous numbers in almost every habitat suitable for life. Although many parasitic species have been extensively studied because of their medical, veterinary or agricultural importance, the most...