Vol. XXIV. No. 3.] 
POPULAR SCIENCE NEWS. 
43 
the fact that the digestive cavity is thus one and the 
same with the cavitj of the body that the group of 
animals wjiich the hydra typifies receives its name, 
the word Coelenterata meaning hidden stomach. 
Thus the bodily structure of the hydra is exceed- 
ingly simple. While in all higher animals, from 
worms to mammals, there is a digestive tract, or 
alimentary canal, separate from the general cavity 
of the body, in the hydra a single cavity suffices. 
Food taken in at the mouth moves about freely in 
this cavity, undergoing digestion the while. Should 
any innutritions matter be swallowed with the f»od, 
it must be passed out of the body by the same open- 
ing that it entered, that is, through the mouth. 
Moreover, in this simple, sack-like animal there are 
no internal organs at all, the work of food-digestion 
being performed by the action of the cells that com- 
pose the walls of the body, and the circulation of 
the fluid product of digestion (blood) being effected 
by the general movements of the body. 
Having thus noticed the general features of the 
hydra, we may now pass to a more detailed exami- 
nation. By the use of the microscope it can be seen 
that the body is made up of two layers of cells — an 
outer layer, or ectoderm, and an inner Jaycr, or 
cndoderm. If the cells of the two layers be exam- 
ined and compared, they will be found to differ 
somewhat. While — like all unmodified living cells 
— they consist of minute bits of protoplasm, each 
having a nucleus, those of the ectoderm have a 
different form, and, as experiments show, possess 
difterent active powers, from those of the endsderm. 
If a few ectoderm cells be isolated and examined 
under high magnification, they will be foiXid to be 
drawn out at their inner ends into long processes. 
In the living animal these processes lie between the 
two layers, and extend longitudinally. Now, to 
understand their use, let us observe what happens 
when a hydra, extended at full length and swaying 
its body to and fro in the water, is lightly touched 
by a needle. The body — a quarter of an inch in 
length when extended — is quickly contracted into a 
small rounded mass. The little creature thus pos- 
sesses the 'power of contracting its body to a 
wonderful degree, and it has been found that it is 
the processes of the ectoderm cells in which this 
power of contractility lies. What we learn, then, is 
that these processes have the' same function that 
belongs to muscle-tissue in the higher animals. 
And, as the endoderm cells are not provided with 
these processes, we see that the latter differ from the 
former both in form and in physiological properties. 
We may now examine the endoderm cells. They 
are of an irregularly spherical form, and have scat- 
tered through their substance small grains of a 
green color. It is the possession of cells containing 
this green coloring substance that makes the hydra 
almost unique among animals : for this green mat- 
ter is chlorophyl, the same substance that gives to 
plants their characteristic color. Now, in plants, 
chlorophyl has a very important function : it enables 
the plant to utilize the sunlight in the making of 
starch, sugar, etc., out of things taken from the air 
and soil — as water, carbonic acid, and ammonia. 
The interesting question thus arises, whether chlo- 
rophyl serves the same use in the hydra. This 
point has not been finally determined. It is known 
that the hydra, like other animals, seizes and feeds 
upon organic bodies as food, but whether it is also 
able to derive food-matter from inorganic com- 
pounds, by means of the chlorophyl-grains, is not 
yet known. 
But what is certainly known in regard to the 
endoderm cells is, that they are brought into con- 
tact with the organic compounds swallowed as food 
by the hydra, — since these cells line the stomach- 
cavity, — and seem to digest them. At any rate, the 
food-matter, consisting chiefly of minute animals, 
is gradually absorbed by the living cells, and thus 
the life of the hydra, as an animal, is preserved. 
And here we may point out a biological principle 
of fundamental interest. Any living body, plant or 
animal, is an aggregate of cells, and the iife of the 
body is the in toto life of the cells. It is understood, 
of course, that we are here speaking of life as 
ritalitf/, not as conseioiisiiess. The principle is, that 
life, considered as that state of the body which is 
opposed to death, is the product of the unified life 
of the component cells. 
The biology of the hydra is especially interesting 
in regard to the ways in which the function of 
reproduction is effected. We do not commonly 
think of one animal being derived from another by 
a process of budding, just as one branch of a tree 
grows out from another. Yet this is one of the 
ways in which new generations of hydras are pro- 
duced. The cut shows a young hydra, formed by 
this process of budding, still affixed to the parent 
animal. During the time when they are thus con- 
nected, the body-cavities of the two are continuous, 
so that food swallowed by either is available for the 
nourishment of both. Sometimes . the bud-hydra 
will itself give rise to another, .so that three genera- 
tions of hydras will exist in one body. After a 
time, the buds detach themselves from the parent 
and begin an independent career. 
Reproduction by budding occurs only during the 
summer. At the approach of cold weather another 
process takes place, whereby the hydra perpetuates 
its kind. A small protuberance appears upon the 
trunk, just below the tentacles, and a second, larger, 
rounded growth farther below. Now it has been 
found out that these parts are sexual organs; that 
in the former, male cells are developed, and in the 
latter, an ovum, or female cell. The male cells 
eventually escape from their covering, and, by 
means of vibrating, hair-like processes (called cilia), 
swim through the water to the ovary, or sack con- 
taining the ovum; then, penetrating the wall of the 
ovary, they unite with the ovum, which is then 
capable of developing into a new hydra. But this 
does not take place until the next spring, the fer- 
tilized ovum remaining at the bottom of the pond 
during the winter. 
Let us notice that one method of reproduction 
shown by the hydra is non-sexual, and the other a 
true sexual one; also that these take place alter- 
nately. The same is true of many of the lower 
organisms, both plant and animal, and the whole 
process is spoken of as an alternation of generation. 
The manner in which the ovum develops into a 
full-grown hydra is, briefly stated, as follows : The 
cell divides into two; these grow and, dividing 
again, give rise to four; the procEss continuing, 
eight, sixteen, etc., are successively produced. The 
aggregate of cells thus formed is a rounded, mul- 
berry-like mass, and the embryo hydra is then said 
to be in the morula stage. A little later, the cells 
arrange themselves into two layers, thus passing 
into the gastrula (little stomach) stage. These two 
layers are, respectively, the ectoderm and endoderm. 
The cells composing them, at first pretty much 
alike, soon take on the distinctive characters (noted 
above) of these two layers in the fully developed 
animal. That is to say, the cells become differ- 
entiated into layers, or tissues, having definite and 
characteristic properties. Meanwhile, about an 
opening (the mouth) in the wall of the gastrula, 
the tentacles grow out, and development is complete 
— a new hydra has been formed. 
Now the development, or embryology, of all 
animals is, in its earliest stages, substantially like 
that of the hydra. All begin as a simple cell, and 
pass through the morula and gastrula stages; and 
in all, the cells gradually arrange themselves into 
groups, thus forming tissues. At first, taking the 
case of an animal of high organization, there is no 
muscle, bone, nerve, or other distinct tissue ; but, 
gradually, the undifferentiated cells fall into groups, 
take on distinctive characters, and thus build up the 
complex body. These are the fundamental facts of 
etnbryology. 
Union College, Schenectady, N. Y. 
fOi-iginal in t'opular Svienfe News.\ 
AN ANCIENT INDIAN VILLAGE SITE. 
IIY VVAKREN K. MOOKEIIKAI). 
For Several centuries there flourished in certain 
spots throughout the fertile Ohio Valley, large and 
small towns inhabited by aborigines, who gained 
their subsistence by hunting, fishing, and limited 
agricultural pursuits. Many of these villages 
occupied the same locality year after year; some 
of them might have retained their position at the 
present day but for the settling of the country by 
the whites. Those who study the ancient Indian, 
and who have become expert in field searches, can 
readily distinguish the spots occupied by these 
towns by the refuse — such as broken pottery, flint 
and stone implements, burnt rock, etc. — that thickly 
strews the surface. Often these objects have lain 
exposed to. atmospheric agencies for so many years 
that they present the appearance of the natural sur- 
face rock in color. 
The Indian towns were most numerous in the 
State of Ohio, for it is in her river valleys that we 
find field after field covered with diversified forms of 
rude implements in various stages of manufacture. 
The valley of the Little Miami River, for a distance 
of seventy miles, was occupied by quite a numerous 
people. At Old Town, in Green County, we find 
the first large village site, at the forks of the river, 
where it is swelled to a considerable size by the 
influx of Caesar's Creek. From this point to its 
junction with the Ohio River above Cincinnati, 
towns were located every one or two miles. 
At the station on the Little Miami Railroad 
named Fort Ancient (in honor of a large pre-historic 
earthwork upon the hills above), the largest Indian 
town fouml in the entire valley was once situated. 
The railroad runs parallel with the river for some 
distance, and is two hundred yards east. Extending 
between tlie base of the hills and the river, for a 
distance of half a mile, and having a breadth of 
