a, Collins et al.2 have identified adult stem cells in the mesenchymal tissue of male schistosomes, which underlies the intestinal epithelium. These 'neoblasts' can self-renew through a process that may involve activation of the gene SmfgfrA, which encodes a FGF-receptor-like protein, SmfgfrA. They can also produce daughter cells capable of differentiating into multiple cell types, including muscle and intestinal epithelial cells. b, Schistosomes have a complex life cycle. In their mammalian host (humans or, in the laboratory, mice), they reproduce sexually, with the female parasite producing eggs. The eggs pass into the environment through the host's urine or faeces, eventually hatching to release larval stages that infect an intermediate host, the aquatic snail. It is in snails that the infectious larvae form, and they mature into adult parasites once they have entered their human host.