F. Frank LeFever wrote in message
<7eh4d6$pdc at dfw-ixnews4.ix.netcom.com>...
>>re vertebrate and arthopod inversion: yes, we (speaking for myself,
>anyway, as a vertebrate) have skeletons on the inside, and "they"
>skeletons on the outside; but do you have in mind something more
>profound than that?
>>And yes, there do seem to be common mechanisms involved in brain
>plasticity at the level of memory formation and at the level of
>>F. Frank LeFever, Ph.D.
>New York Neuropsychology Group
My impression is that "vertebrate/invertebrate inversion" is
related to the dorsal vs ventral location of the main longitudinal
nerve cord, possibly adding the location of the heart (vertebrates
have dorsal nervous system, ventral heart -- some invertebrates
have the opposite). The same argument has been used to
"explain" the decussation of vertebrate central/peripheral
connections -- the left brain connected to the right body.
I think that all the developmental, molecular biological, genetic,
and evolutionary work in the last 150 years or so argues
against any simple "inversion" origin of the vertebrates.