Re: Why hasnt 360 degree vision stood the test of time ?

Your assumption that animals need the ability to detect their surroundings 
in 360 degrees is correct, but it doesn't necessarily have to be vision.  
The first animals to develop eyes lived in the ocean, where vision is 
limited due to the low level of light.  Those organims most likely used 
vision to detect their environment over short distances.  Smell, hearing, 
and touch (mainly the lateral line of fishes) were probably more useful for 
detecting their environment over longer distances and in 360 degrees.  Also, 
the position of the eyes on a fishes skull and the shape and characteristics 
of the fish eye give it an almost 360 degree field of view.  Basically, the 
fish didn't evolve 3 or 4 eyes because they didn't need them.

So, what about animals on land?  Well, these organisms have basically the 
same body plan as the aquatic organisms they evolved from.  Because the 
ancestors of terrestrial animals only had two eyes, they will have two eyes.  
Though terrestrial animals have many modifications that aquatic animals 
don't, I think you'll agree that developing eyes out of the back of our 
skulls is much more difficult than evolving hair.