The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1898-01-16

mentary tract, as it does in every YER
tebrate without exception, it reverseS
this position. Its long chain of ganglia,
linked by nerve cord, runs along the
! lower side of the body, instead of along
the back. And, TO make the matter
worse. at its anterior end the cord di-
vides, and passes as a loop about the
oesophagus of the worm, to terminate
in a final ganglion, which takes the
place of a brain, and lies where a brain
Should, according to vertebrate Gus
toms, on the upper side of the body.
SO very general is this arrangement
of the nervous system among the inver-
tebrates, and so universal the dorsal ar
rangementS among VertebrateS, that
this discrepancy may be said to repre-
sent the most important of those miss
ing links about which people are so
fond of talking. It is a link very far
removed in the chain from where the
popular conception places it.
Notwithstanding this discrepancy,
Professor Minot, along with e host of
other naturalists, is disposed to think
that these worms are the true ancestors
of the vertebrates. The discrepancy in
the nervous system is explained by
supposing that the terminal ganglion
bees me degenerated as the animal
evolved, its place being taken by the
one next it in the chain, which lies,
like all the other, on the vertebral side;
and that finally the animal body as
a whole reversed its position, so that
ultimately it became customary Tor it
to move about with its nervous side
upDermost. For an aquatic worm,
wriggling about in more or less indiffer-
ent attitudes. to make such a change
does not seem very unreasonable.
CRUSTACEANS OUR ANCESTORS.
There are those at the meeting, how
ever, who demur very strongly at this
view OF the case; in particular Dr. Gas
kill, the famous London anatomist, who
has q theory of his own in the matter to
defend. This theory supposes that not
the worms, bat the jointed creatures,
such as crabs. Holsters and insects, are
the true ancestors we are searching for.
These creatures present the same diff
Guilty regarding the nervous system
that is shown by the worms. but Dr.
Gasiill meets it in q. novel way. He be-
lieves that the foremost ganglion. which
does service for brains in the insect, is
the direct forerunner of the brains of
all higher creatures. He thinks that the
rest of the nervous system, from being
in the first place merely looped about
the oesophagus, came finally, as it de-
veloped, 20 surround the entire digestive
tract, until that important structure
ceased to be of any use, remaining as a
mere rudimentafy cavity within the
brain of the vertebrate. One hears
sometimes in unscientific circles of a
man having his brains in his stomach;
but, according to DR.. Gaskill, everyone
has the rudiment of a stomach in his
brain. Meantime, of course. a new ali
mentary tract was developed to take
the place of the old one, whose domain
had been encroached upon by the grow
ing nervous system.
The evolutionist, however, is little
guided by mere external appearances,
and he finds no difficulty in bridging the
gap between a worn-like fish and a
fish in armor. For that matter, he finds
no great stumbling block between the
lowest fish and man Understanding
at all to be compared to the puzzle sup
piled by the difference in nervous sys-
tenn above outlined. which is the real
barrier between the true worm and the
worm-like fish. Some day the students
of lower forms of life will bridge this
gap, through observation of the devel-
opment of the embryos of the creatures
under discussion. Until then we cannot
be sure whether the humble earth
wcrm or the busy bee is our nearer kin.
But it is q helpful check upon ones
pride of lineage to reflect that one or
the other of these, or at any rate some
other creature equally humble, was our
unidentified ancestor