SESSILE ORGANISMS MUST BE READY FOR LOVE

As a general trend, sessile organisms are monoecious (hermaphrodites) and mobile organisms are diecious (having separate males and females).  This makes a lot of sense!  Practically speaking, if you don’t move, your chances of finding a mate of the appropriate gender are far slimmer than those who are on the move.  So, when you are sessile and DO find a mate you want to insure you have the correct gametes (eggs or sperm) available.  By having both eggs and sperm (as in hermaphrodites) you are ready to mate with that special someone when they are available.