The annelids include the species of worms best known in Britain, namely the earthworms, the lug worm which is used for bait, and the leeches. The earthworms have bristles which point backwards and help it to force its way through the soil, but nothing resembling legs. The most formidable to man is the hook worm Ankylostoma. It was this animal rather than General Grant which won the American Civil War. Ankylostoma needs warmth and moisture for its larvae. A much more respectable phylum of worms is called the Nemertines. The nemertines need a heart to supply oxygen to their vigorous muscles, and have even got red blood, and, for worms, quite a good nervous system. he polyp's way of life, like that of the worm, has been adopted by animals of very different structures. The most successful phylum of this kind, called the Polyzoa, has done their share of rock-building, though less than the corals.