APB1L as 
Tho yolk, that homogeneous substance which 
fills the vitelline membrane, in which swim 
the germiuative vesicle and germinative dot, 
must undergo a very remarkable change 
before it car) give rise to tho new individual. 
It is self-kncading, broken by the process of 
its own growth into a smaller or larger num¬ 
ber of distinct fragments. 
THE PROCESS KNOWN AS "SEGMENTATION.” 
This breaking up of the whole substance 
which siroujat'es disintegration ends in a 
new individual, does not receive the direct 
transmission of inherited qualities, for as I 
have said, that eg * arises in maternal organ¬ 
ism, and has a life and growth of its own 
before the act. of fecundation takes place. 
Through that net of fecundation the impres¬ 
sion must be made by which these inherited 
qualities arc received and transmitted to the 
new individual. Where the new individual 
reproduces the maternal features only, or 
f p/, * 11 vo« t>h rive Mr-ri at if rf the 1 ; -o 
EARLY LIFE IN THE EGG 
Lecture before the Museum of Compara¬ 
tive Zoology, Cambridge, Mass., by Prof. 
Louis Agassiz. 
Having seen something of the great diver- 
characterizing different 
sitv among the eggs, 
classes of the animal kingdom, wc may now I 
consider the functions of the egg itself—that J 
is, the part which eggs take in the history of 
generation. I cannot dwell too emphatically j 
upon the fact that eggs are produced and 
grow without any agency of the male animal. 
They arc a production of tho female organism. 
So true is this that the ovarian egg may be j 
found in animals before they have reached 
maturity ; before they have completed their 
physical growth—nay, ovarian eggs have 
oven been observed hi the embryo before 
birth. Neither do successive generations 
begin with the birth of new individuals, but 
with the formation of the egg from which 
these individuals proceed. Wc must look, 
then, upon the egg as the starting point of 
the complicated structure of the adult being. 
It is, as it were, a sieve t hrough which the 
qualities transmitted by parents to their off¬ 
spring are sifted. Whatever peculiarity 
there may bo hi the new being, has its founda¬ 
tion in the egg. Within those narrow limits 
are circumscribed all tho conditions of 
change ; and therefore it is of paramount 
importance to know what tho egg receives 
and what it transmits. Wo cannot investi¬ 
gate this part of the subject too closely. It 
is of vital importance to the question. And 
yet I have not seen it discussed in connection 
with tho various explanations of the origin 
and diversity of life recently attempted. 
The egg arises in the maternal organism 
without co-operation of the other sex, and it 
can transmit only what it receives directly 
from the maternal organism, or from tho 
paternal organism through contact with the 
maternal, or from ancestors through one or 
both. Ther.j has never yet been recorded an 
instance in which an egg has grown to be 
anything but a. being similar to its parents, 
and yet the possibilities of modification arc 
so numerous under those conditions, and the 
range of variation so great, as to make us 
wonder the more at the constancy of types. 
MODIFICATIONS DUE TO ANCESTRY AND SEX. 
Suppose, for instance, that a male and 
female (I deal here with the subject in the 
most general way without reference to any 
particular species or type of animal) produce 
three new individuals. The, three, may hca.ll 
males or all female#, or two may lie females 
and tho third a male, or vie c verm. The 
three may all resemble the mother, have her 
features, her stature, her physical tendencies 
generally; or they may all resemble the 
father; or one or two of the three may 
resemble the mother, the third may resemble 
the father; or only one may resemble the 
mother, the other two being like the fat,her; 
or they may all combine the physical fea¬ 
tures of both parent s, Or one may present 
such a combination and the others follow dis¬ 
tinctly one or the other parent. Any one 
case, bo the offspring more or less numerous, 
will show us what, a variety of modifications 
arises merely from the contact, of two beings 
to produce one or more new individuals. But. 
the matter is still further complicated. These 
new individuals have had a grandfather and 
grandmother on the maternal side, and a 
grandfather aud grandmother on the pater¬ 
nal side. You arc all familiar with the 
singular fact, well known to us in the human 
family, and often observed throughout the 
whole animal kingdom, that children may 
not resemble tlicir parents at all, but be 
strikingly like tlicir grandparents. Thus in 
the new individuals the same combinations 
which might arise from their immediate 
progenitors may also pass to them from a 
previous generation, from their grandparents, 
that every separate particle, owing to its 
diminutive size, is difficult to microscopic 
observation, even under very high power, 
each such part icle seems like a cell, and may 
indeed be considered as a cell. This self- 
division of the yolk ends in an accumulation 
of cells which differ from those of the initia¬ 
tive yolk, and arc. the basis for the formation 
of the new being ; the material, in fact, out 
of which the new being is to he built . 
If wc now compare the egg of a reptile, 
that of our common snapping-turtle for in¬ 
stance, with the mammalian egg, we find 
that the process of segmentation differs some¬ 
what,, and does not penetrate the whole sub¬ 
stance in the same manner. A portion of 
the surface of the yolk becomes plowed as it 
were by furrows at right angles with each 
other. (See Fig. A) These furrows do not 
extend over the whole surface, but encroach 
upon it, only for a certain circumscribed urea, 
the remainder of the yolk remaining in its 
original condition of yolk cells, while the fur¬ 
rowed area rests upon it jis n skin or layer. 
There is now a difference between above and 
below, marked by the distinct character of 
the upper and lower portion of the yolk. (See 
Fig. 4.) We shall presently perceive a differ¬ 
ence between right and left, between front 
and back also. 
In the eggs of the frogs and toads there is 
still another mode of segmentation. The 
yolk divides, as in the mammalian egg, into 
halves. But only one of these halves pro¬ 
ceeds with the self-division and multiplies 
itself into an indefinite number of cell like 
particles. The other half of the yolk remains 
unchanged. (See Fig. 5.) 
SACRIFICES NECESSARY TO THESE STUDIES. 
You "ill easily understand how difficult it 
has been for embryologists to put together in 
their true sequence these phases of develop¬ 
ment. Not only must the exceeding diffi¬ 
culty of the microscopic, observation he con¬ 
sidered, but also the fact that, in order to 
Flu. l.— Egg ok Mammal di king Slumlnta- 
TION INTO TWO PARTS. 
of descent., the case may seem at first sight 
more simple ; but when wc analyze it in all 
its bearings, we shall see that there is matter 
enough for wonder, and that we as yet, know 
almost nothing about the mysterious problem 
of life. What can there be of a material 
nature transmitted through these bodies 
called eggs, themselves composed of the sim¬ 
plest. material elements and arising in the 
female organism without co-operation of the 
male ; what influence can there be, 1 repeat, 
by which all peculiarities of ancestry belong¬ 
ing to either sex arc brought down from 
generation to generation ? 
COMPLICATIONS OF THE 0R0WIN0 ECO. 
The egg, as we have seen, is in its incipient, 
condition, only an organic granule arising 
fecundation ; others in which it is always 
subsequent to fecundation ; in no animal is 
the process known to be completed without 
fecundation. Neither docs it take pluce in 
nil animals in the same manner. 
Take, for instance, the highly magnified 
yolk af a mammalian egg with the germina¬ 
tive dots already formed on the side. The 
vitelline membrane surrounding such a yolk 
Is rather thicker than a bird's egg, and forms 
a sort of transparent zone outside of t he yolk. 
When the process of segmentation begins, 
the yolk shrinks slightly* upon i'si-lf and no 
longer fills tho vitelline membrane complete¬ 
ly, Presently a slight indentation becomes 
visible on the one side of the yolk, and 
another corresponding to it on t he opposite 
side. This indentation grows deeper and 
deeper until it cuts tho yolk through, and 
ends in its total division into two halves, the 
halves remaining, however, in close contact, 
(See Pig. 1.) While this process goes on, the 
germinntivc vesicle vanishes, if indeed it has 
not disappeared before. In some animals this 
vesicle is dissolved before the segmentation 
begins; in others during the process. Tho 
division of the yolk in halves being completed, 
the same change begins now in the two 
halves. Indentations are seen on either side 
of each half, and these indentations deepen 
till they meet and sever the two masses of 
yolk ; and now, where we had one yolk mass, 
we have four distinct lumps side by* side.; 
they become rounded in form, and look like 
four soft balls. (See Fig. 2.) 
Within the vitelline membrane, occasionally 
it would seem that the whole yolk is uot 
taken in ; there are sometimes little frag¬ 
ments left out from the larger masses. 
Whether these separate balls <>f yolk have 
Fig. 2.— Egg of Mammal Undergoing Feu 
MENTATION INTO EIGHT PARTS. 
between the structural cell* of the ovaiy. It 
grows there and acquires a remarkable com¬ 
plication before it has completed its succes¬ 
sive phases as an egg. Not until it has 
reached the state which I have described us 
1 hat of the perfect egg does it receive the 
contact of the spermatic cells from which 
dates the. formation of a new being, either 
male or female. This in itself is a strange 
thing—that a mother produces, not necessa¬ 
rily' a being like herself, but quite as often 
beings so unlike herself in structure as to be 
endowed with all the peculiarities of the 
male sex. In tho originating of a new sne- 
BRIEF NOTES 
To Prevent Paste from Molding and sour¬ 
ing, add a little carbolic acid to it. 
To Preserve Natural Flowers with wax, 
melt paraffine, and dip the flowers into it 
very* carefully*. 
Excellent Fed Stativy Wa% is made by 
mixing 1 lb, shellac, 1 lb. Venice turpentine, 
i,.;' lb. chalk and }4 lb. English vermilion. 
To Prevent Glue from Cracking, it i* 
recommended to use a very small portion of 
gly’cerine, incorporating the glue in it befoie 
applying to wood. 
A Glue that will Stand Exposure to W et 
is made of caoutchouc, 15 or 21) grains, chloro¬ 
form. 2 fluid ounces ; dissolve and add half 
Ida. h.—E gg of Turtle During Segmenta¬ 
tion. 
cics this double series of influence must be 
included and combined iu the proportions 
necessary to produce a being differing from 
all foregone species, and capable of maintain¬ 
ing its pattern generation after generation. 
There is one feature in the grow th of the 
egg of which 1 have as yet said nothing. 
Fig. 5.—Egg of Batraohians. 
envelopes of their own is a question difficult 
to decide. The most skillful naturalists differ 
about it. Tho original yolk being thus 
divided iu four, tho same process goes on till 
the four are divided into eight, the eight into 
sixteen, the sixteen into thirty-two, the thir¬ 
ty-two into sixty-four, 
