How many vertebrates lack eye lenses? Fish have them as do all
tetrapods that I know of. So maybe the answer is zero. There are
some species that have greatly reduced eyes and presumably greatly
reduced optic tracts. Still, so many other central systems
decussate, that it seems unlikely that something like the formation
of a lens could account for crossed visual pathways.
rlh
>maxwell wrote:
>snip
>>> Well, yes, I did as much. I'll note that your earlier
>> mention of the probable phylogenic constraints,
>> that resulted in decussations, consistent with current
>> ontogenic molecular findings, are another
>> pleasant spot of actual science amidst the folderol.
>> ...Which apparently evoked no further interest, alas.
>>>>[Hammond]
>Is it plausible that decussation originated in
>the fact that a lens "reverses" it's image, and the
>easiest way to correct this unwanted optical circumstance
>would be to simply "reverse" the wiring somewhere else
>in the system. To wit: do animals without eye lenses normally
>exhibit a major decussation in the CNS, or is this
>reserved only for animals with lenses?
>>>--
>BE SURE TO VISIT MY WEBSITE, BELOW:
>-----------------------------------------------------------
>George Hammond, M.S. Physics
>Email: ghammond at mediaone.net>Website: http://people.ne.mediaone.net/ghammond/index.html>-----------------------------------------------------------
--
Richard L. Hall, Ph.D.
Comparative Animal Physiologist
University of the Virgin Islands
2 John Brewers Bay
St. Thomas, U.S.V.I. 00802
340-693-1386
340-693-1385 FAX
rhall at uvi.edu
"Live life on the edge...the view is always better" rlh
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