Proposing for the first time that the reproductive system controls major differences in regulation of gene expression and behavior among individuals in single-celled eukaryotes, Grant and Dunham (7) put forward the intriguing "obvious" role of the germ plasm. Non-mutant organisms are encoded in the genome. Since germ line loss and faulty maternal expression can lead to what we call behavioral phenotypes (that is, abnormal elicitation of a complex physiological response) in the heterozygote 66c