[Annelida] metamerism

Geoff Read via annelida%40net.bio.net (by g.read from niwa.co.nz)
Tue Nov 11 15:56:04 EST 2008


Let us go back a way. Here is  Lankester's view of metamerism.

Lankester, E.R. (1904). The Structure and Classification of the
Arthropoda. Quarterly Journal of Microscopical Science s2-47: 523-582 

"The body of the Arthropoda is more or less clearly divided
into a series of rings, segments, or somites, which can be
shown to be repetitions one of another, possessing identical
parts and organs which may be larger or smaller, modified
in shape or altogether suppressed in one somite as compared
with another. A similar constitution of the body is more
clearly seen in the Chaetopod worms. In the Vertebrata also
a repetition of units of structure (myotomes, vertebrae, etc.) —
which is essentially of the same nature as the repetition in
Arthropods and Chaetopods, but in many respects subject to
peculiar developments—is observed. The name "metamerism"
has been given to this structural phenomenon because
the " meres," or repeated units, follow one another in
line."

There is much, much more, showing the joy of morphologists of the time
in inventing terminology that is obfuscating rather than illuminating,
but one can see from the above that metamerism is a relatively abstract
term, that we can debate as to its precise meaning and scope. Perhaps it
would be best to stay with feet on the ground and use easily understood
words for observable things such as segmentation.  Alternatively, bring
back Mesmerism, and all the other 'isms .... 

Geoff


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 Geoff Read <g.read from niwa.co.nz>
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  http://www.niwascience.co.nz/ncabb/
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