Hence they invent mouth aprons and food privies , while having sex in public .
An unspecified future human species ( one of the Eighteenth Men 's predecessors on Neptune ) is presented as having an attitude to nutrition analogous to the First Men 's sexual puritanism .
First Men invent mouth aprons and food privies , while having sex in public .
An unspecified future human species ( one of the Eighteenth Men 's predecessors on Neptune ) is presented as having an attitude to nutrition analogous to the First Men 's sexual puritanism .