It has recently been demonstrated that activity of the bag cells an identified gioup of neurosecretory neurons in Aplysia, leleases a substance that causes egg laying. A cytologic analysis of the ovotestis, before and after administration of the bag cell extract, suggests that one function of the bag cell substance is to cause the small muscle cells that surround each follicle of the ovotestis to contract, thus expelling ripe oocytes from the ovotestis ind beginning them on then journey through the oviduet