[
Nature,
1991]
Populations of the soil nematode Caenorhabditis elegans normally consist almost exclusively of self-fertilizing hermaphrodites. The animal first matures about 300 sperm and then a much larger number of oocytes (eggs). Nearly every sperm is used to fertilize an egg and so the maximum fecundity is around 300. Why doesn't the nematode mature more sperm and thus increase its fecundity? In a paper in the Proceedings of the Royal Society (B246, 19-24; 1991), J. Hodgkin and T.M. Barnes provide both an elegant answer and a rare insight into the mechanistic basis of an important life-history trade-off.