left-right reversal of CNS: Why?

[Henry M. Wieman]

Why does the CNS have right and left reversed in relation to rest of the body?

Failing an answer to that, What is "lowest" animal in which the reversal is 
found? 

Specifically, do any invertebrates show the reversal?


   	Henry M. Wieman          | "Can you answer? Yes I can!
        wiemanh at ma.ultranet.com  |  But what would be the answer,
        Call me Hank             |  To the Answer Man?"
                                 |       -Robert Hunter in St. Stephen