New-York tribune., 1873-05-24
THE RADIATES.
NINTH LECTURE BY PROF. AGAssIz.


MNs-STBrKING ILLUSTRATIONS.
fPnOM AN OCCASIONAL RESPONDENT or THE TRIBUNBl
CAMBRIDGE. Mass, May 29.-The following
lecture was delivered May by Prof Agassz before the
Museum OF Comparative Zoology.
variety OF specimens OF coral which have here for
exhibition today will show You how prolific is the pro-
cess OF budding; indeed the multiplication of indvdu-
ais by this mode OF reproduction is much rapid
than by eggs. Here gOrgOnia branching coral with
horny axis the surface OF which are thousands OF
individuals small that except close examination you
hardly distinguish them from the other Yet this
countless community is the growth from single ind
vidual, born from an egg, and then repro
ducing itself al n6nit,sm by budding. Coral
animals arc not however always small nor are theY
always compound. Here is Fuuga which always grows
singly and attains, you considerable SIZE Inc
Fungia from eggs and feed Here Is species
Of Pories which like to show in illustration Of my
subject because know its history aud have traced IL
myself. have seen the egg laid, have watched the
little coral as free being swimming about in the water,
and later when It chose its reStingpace and became
attached 70 a solid foundation. From that time
II begins 70 put out individuals buds, and grows
gradually such compound stock as the one you are
examining. Here specimen Of another kind OF com
munity MadrepOrs, born also originally from single
egg 1t striking fact not to be overlooked that the
number OF coral animals thus remaining in organic con-
nection with each other much more numerous
than those hatched in the ocean from eggs Indeed did
the latter compare in number and rapdty Of increase
with the former, the bottom would be paved with
them. No doubt, with coral eggs, as with the
delicate eggs Of many Of the lower animals,
comparatively few Of those which are laid sur
vve. They arc the prey Of hosts OF crea-
lures and the extraordinary power of multiplication
in OF the lower animals is doubt in proportion
20 the dangers which beset their progeny. The fresh
water gordius, the socalled "horsehalr worm" for
instance (named from common superstition growing
out OF It's resemblance to hair and leading to the idea
that a single horse-har may be transformed into a
worm) lays about 100000 eggs And yet these animals
very Did all their eggs TO maturity our
brooks and ponds would be full Of them The history Of
these animals is most curious. They hatched in the
water from eggs. They leave the water after time,
however; 90 wet days into the grass creep along
the legs of torpid grasshoppers, enter their abdominal
cavity and undergo further transformation parasitic
From this living prison they then escape, return
20 the water and end their varied existence as the long,
threadlike worms which have been mistaken for living
and moving hairs
THE CLASS THAT MULTIPLIEs DIVISION.
But this is DEPRESSION from cOrals wish now to
show you that the representatives OF this class multiply
BY self division well by eggs and by budding and
that the process Of division with them does
sarly lead to the separation and breaking of OF ndi
vduals from the parent stock but may only contribute
to an increase Of the community. Each individual on
such stock is represented in the beginning by a
round, symmetrical body with internal radating par
ttons such characterize all coras But each in-
dividual grows IL rises until it has attained maximum
which 1t never exceeds, as in most species Of Astrea
In this case the individual animals separate more or
less in their upper part until the interval wide enough
10 support poyp, which arises then between those
that have already completed their transverse growth
though they may still increase in hight In other species
the individual animals enlarge, they spread also and
the opening instead OF remaining circular tendency
20 elongate and become Oblong.
Then this oDlOng opening contracts In the middle
and MORE till the sides meet at that point and
where we had mouth now have two each with
independent Of tentacles; two heads it
body. In certain species these two mouths may
again divide by the same process Of enlargement aud
contraction, and presently larger number OF mouths
present themselves instead OF the first two and
till we have several heads original body.
Such group may become free and be in time the bases
OF a community There various modes Of self
division among corals beside the have described.
In some, individuals arise from the thickenng Of
the wall Of the original being.
In other cases the wall remains thin but the cavity
OF the parent animal widens and the individuals
produced from the enlarged cavity. In the case
represented, we have Diplora, a kind OF brain coral
In this genus the trenches the surface which repre-
sent the coDOined cavities Of the different animals that
have arisen by division and which are indeed only the
external openings Of these cavities, remain while
the partition walls dividing the animals from each other
are of very unequal thickness At every point where
the partition enlarges 1t opens; depression in the
thickness Of the partition forms new stomach; new
tentaces arise and in short. complete organism
appears exactly the OF the Astrea represented
in the first Of the Illustrations
In the other instance we have common mandrina,
in which the internal cavity Of single animal becomes
so wide that there for two where there but
before The internal parts divide and give rise to
second organism which then opens the surface side
side by side with the frs the dividing PARTITION retain
ing all the while the same thickness.
Here then animals remaining united by the lower
parts of their body, but having distinct heads and dis
nct internal cavities yet in which the juices elaborated
by digestion one individual feed the stock.
This may till hundreds Of thousands nay millions,
individuals share the result OF functions Of life and
digestion performed only by certain limited number of
the community. Let not forget that sometimes mon
strosites in the higher animals and in the human
family give exceptional facts not unlike this normal
development radates Occasionally human body is
with two heads; two perfect human bodies
born and ndissouby connected in the case OF the
5smese twins But in such cases is probable though
absolutely demonstrated that the abnormal birth is
due to the uxtaposton soldering together of the
eggs and not TO the evolution Of the individuals om
the same egg.
QUESTION oP INDIVIDUALITY.
The problem Of individuality in connection with the
fact OF a compound existence in less numerous
communities, is perpexing We associate the idea
OF individuality with that Of complete independence
in all the functions of life. Yet here we have millions OF
individuals bound together in life, and dis
tnct nevertheless from each other One thing is
tain whether such coral animal, born from egg,
multipes by budding division whether the ndiVidu
ais so formed drop of TO form colonies remain
connected with the parent individual the product Of
either OF these processes is strueturay speaking
acy the the product OF an egg Different as is
the mode OF reproduction the result Is Identical And
here again It seems 10 me- we have evidence that
.ha,ayr ba tho reans nv which Nature multplieg her