by Elio — Some­thing there is that likes to mull over sym­bioses. In­deed, what is more en­joy­able to con­tem­plate than the re­la­tion­ship be­tween two or­gan­isms? The an­swer? One that in­volves three, or four, or even more. Not that this is un­usual, just that it's al­ways ex­cit­ing. Here are two ex­am­ples.