New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1873-05-31
VITAL TRANSFORMATIONS.
TENTH LECTURE OF PROF. AGASSIZ.


OBSERVATION-DISCLOSURES SIMILARITY OF ALL
EMBRYONIC ANIMAL FORMS
frRoM An OCCASIONAL CORRESPONDENT OF THE TRIBUNEI
CAMBRIDGE, Mass, May 3O.-The following
lecture was delivered by PROT Agassz on the 18th inst
before the Museum OF Comparative Zoology
Our last lecture brought the subject OF "Alter
nate Generation" as another mode Of multiplication
among animals At first SIGHT this alienation OF animal
forms arising from each other successive generations,
and vet differing entirely Ia external aspect seems like
astartling deviation from the original type and sug
xests ready explanation OF the diversity among living
beings. But closer examination we find that these
alterations are but the oscillations OF prescribed
cycle confined within given limits and returning with
unfang regularity to the starting point / have DOT
time explain tue details OF this curious mode OF TO
production. out will at least give you so much o' 'no
facts a. will enable you understand their oeariuS
upon the question OF maintenance OF VPe' 1ncJ "'o
exceedingly suggestive. Indeed the study OF tue
Radiatcs IN general and OF Jellynshes In particular
of the most interesting in the whole neld OF Aoooey
Without a thorough knowledge OF these animals and
their transformations zoOogst at the present time
can form correct views of the leading questions IN MS
own department OF science. The naturalist who Is not
perfeeiy familiar not only with the anatomy OF these
animals with their comparative structure, from that OF
the simplcsf bud OF POlyp to that OF the most comp
Gated Echino1orm, but also with their multiplication
and growth whether from budding, selEdiylsOn' or
eggs and with history OF their succession In Seoog
cal ages has no foundation for discussion respecting
the order OF introduction OF animals upon earth, nor
can ne understand the meaning OF that order with refer
ence 10 the existing diversity OF organic life. These
not subjects O. TO deoded by argument but by knowl
edge DriOri opinions about them are futile The I'M
pOrtaRce the Rldiates u connection with these nyes
legations fact that the best BIOLOGISTS and
paIpOntoogsts OF our have made them the object
Of their most ear ful research
GROWTH AND REPRODUCTION OF TIE RADIATEs
To sebold. whose Investigations on various subjects
have REQUIRED often aud naturally in the course OF
lectures after him, to Sars the Swedish natur-
as seeuStgup the Danish investigator, aad to Du-
jardin the French zo0logist first knowledge
OF the curious phenomena, known alternate genera
tons Since their time many younger investigators
have added great deal to knowledge OF the modes
of growth aud reproduction among Radaes but tn csc
men opened the ground aud like 20 recall their names
for apt the later and richer harvest 20 forget
by whom the seed was really sown.
Ihave already shown you that Corals Jeyshes Star
fishes and seaurchins, or, naturalists call them
POyps wiz coras OF all sorts, sea-anemones. and the
hkel Acaleph 0ellyfshes aud hydrOdsl, Echinoderms
isar-6shes seiurehins. and hoOthurans), constitute
unity. from q structural point OF view Imean by TINS
that they are all built the plan OF structure,
aud can compared in all their parts and reduced to
one organic formula Their anatomy differs in oompli
cation proportion aud distribution OF parts but not in
essential features They constitute structural unity just
IA Vertebrates, whether fish, reptile bird mammal
constitute structural unity being respectively built
upon the same plan. way the three classes
Radiates exhibit plan, less elaborated;
simplest In POlyPs more complex in the Acalephs and
reaching the highest degree OF complication in the Ech
Dodcrms. Now, wherever 1ud unity Of structure we
md unity OF development; and shall show you that
this lowest type OF the animal kingdom the Radates,
has one mode of development to all its classes
AS the highest type OF the animal kingdom, the Verte
hrates has also mode OF development common to all
ITS classes
TIE CHANGES PORN OF A JELLYFIsH.
But before enter upon this wide field OF com
parison and generalization, let look at the facts
Of alternate generation. Our common jely-fsh has
four nshaped Oyaries grouped that when
TOUCHDOWN upon the disk Of the iellyhsh from above
they have the appearance OF In these Ovares
tbe eggs formed. From the ovaries the pass
into the central cavity OF the body. and ind their
way out through the mouth into the water.
When first dropped from the ovarY such
egg is little sphere, filed with transparent fluid con-
tanning germinative vesce and germInative dot This
transparent yOk OF light color in the species OF
which am speaking. becomes rapidly more Opaque
Presently the process Of augmentation described IN
former lecture begins The yolk divides in halves into
four eight sixteen, thrtytwo parts, and so on till the
little sphere Is completely kneaded and broken into
the mulberry like body so well known TO naturasts
the final phase Of augmentation. This body becomes
hollow peculiar cells collect upon its circumference,
and put out what called vibratile ciafne highly
movable threads almost like feathery dOwnOver the
whole surface. The envelope gradually thins out
20 form a mouth. The swimming yOlk, while freely
moving in the water, by means Of these ella
keeps itself constantly turning and rolling in every
direction, forward, backward, and sideways. its sub
stance assuming steadily more the structure OF
Hydrod. Presently it ceased to be quite round and
becomes oblong pearshaped. depression takes
place at one end, deepening gradually; and as It
deepen the ella become less active the rotating rest
little being sackens It's speed pauses settles on the
end opposite the depression, and becomes fixed The
upper end the margin Of internal cavity formed by
the depression spreads in four directions protrudes
four folds as 1t were. These folds change TO tentaces
which multiply from g. from TO 16 from 10 to 49,
ana so we have little polyplike being much like
a seaanemone; with a digestive cavity, a fringe
of tentacles and a somewhat spreading base
IL presently outgrows this phase the body eongates
and in proportion in hight, the internal cavity
deepens tubeke through the center OF the body Next
several OF transverse constructions formed across
the body whole length; showing themselves as
sghtly projecting folds the surface, az regular dis
from bottom Of the animal These folds OF
constructions deepen toward the axis, tall at last the
whole body divided into pile OF saucerhke disks
connected together only in the middle. Every such disk
scaOped around the edge and at TINS stage OF
the development the top OF the body with its wreath OF
rates from the pile and as u does, II capsZes turns us
GRAFTON jeyhshes as the close OF this strange story
UNITY oP ANIMALS APPARESTLr DIFFERENT
The different phases Of this sequence Of development
were known to naturalsts before the connection was
detected The little pOlypnke animal which 1 FIRST
described was supposed to he particular kind Of polyp
and WAS called Scyphosoma; the next phase, when the
body had become CONSTRUCTED and undergoing its
transformation into disks was also known, ana In TINS
stage OF development It had IKE the Scy26oSt ann
stroba; and the scallOped disks had been observed