The sun. [volume] (New York [N.Y.]) 1833-1916, 1899-02-26

In the third chapter OF this volume the an
cestral chain Of man Is traced with the help
OF diagrams which represent our present
knowledge Of our descent. For simpllcity's
sake the many side issues. or branches which
lead to groups not In the main line OF our
Genealogy. are left out. or merely indicated.
Many OF the stages are, OF course. hypothetical.
arrived at by the study Of comparative anatomy
and ontoReny; but an example for each o!
them has been taken from those living or fossil
creatures which seem to be their nearest
representatives
The most remote ancestors OF all living or
ganisms were beings Of the simplest imagin-
able kind. to wit: organisms without organs.
like the still existing monera. Each consisted
OF a simple granule OF protoplasm. a structure
less mass OF albuminous matter. or plasson.
like the recent'chromaceB and bacteria. The
morphological value Of these beings Is not yet
that OF a cell. but is that Of a cytode. or cell
without a nucleus. Cytoplasm and nucleus
we're still undifferentiated In the second
! stage Of evolution we encounter the simple aud
single cell. II bit Of protoplasm with n nucleus.
Such unicellular organisms are still very com
mon. The amPbR are their simplest repre-
beings is the same as that of the egg OF any
animal, The naked egg cells of, the sponges
Observation-Disclosures from amGhg. Tie same re.
mark APPLIES to the egg. eel OF, man himself in
lis early stages, before II IL lnclDSe0 In a mem
hrane. The first unicellnlar organisms arose
from moHera. through differentiation Of the
inner nucens from the outer protorlosm.
Repeated division OF the unicellular organism
produces the synamTbium. or community Of
amGoR. provided the divisional products or
scatter. but remain together. The existence
Of such a cpnoDium.. n number Of equal and
loosely CONNECTED cells. as "A separate, stage in
probable. by the fact that the eggs Of all ami
mails undergo. after .ferttlization. such n pro-
! nnGS nf TaHnDtpI GnlI-IlyIainn nr - pleu y "a fgn ~
until the single egg cell Is transformed into n
heap Of cells closely attached together. not nm
Ike a mulberry nngiuidJ: hence tho morula
stage In ontoGeny. The morula Of most ami
mails further changes into a bidsrd0. n hollow
hall hlIed with iluid. the val being formed by
a as sIin TsIsr layer Of G %n5i ,hs G ,nn e frn, oT seTmi;
by the action. Of the, cells, they. conveying
nourishing fluid into the interior Of the whole
forced toward the surface. The blastula Of
most invertebrata Is possessed Of fine ellie, or
advance IN the water. The blastula OF most
animals assumes new larval form, called gas
are that a portion OF the blastoderm by in
vngina;ion converts, the bIastuIa into a cup
with double walls t%nclqslnG q new cavity the
In. obliterates the original inner cavity Of the
h%lastula, The outer layer Of the blaStula is the
into earh other at the blastopolus, or opening
OF the duct cavity, The blastula is u stage in
the embryonic development q The various
that Of the platodes. or fiat worms. Is. to
q large extent. ,hypothetical These arc
long body, furnished with cilie. with "a print
tive nervous system. and with simple sensory
and reproductive organs. but still without aP-
lendages. body cavity, vent and blood vessels.
The nearest Lying representatives of such
creatures are the acGious turbellariums, for
creature. The nexthlgher stage is represented
by such low animals as the gastricha, which