Charles Wesley Hargitt.

Outlines of general biology ; an introductory laboratory manual online

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the animal assume the expanded condition? Which is the
part to first assume the expanded condition? Note that
in some cases there is no stalk attached to the animals. How
do they behave when this is the case? Vorticella may
separate from its stalk and become free-swimming for a time.
During this period a second row of cilia develops about the
base of the bell, to aid in locomotion. (In some cases this
separation from the stalk is not normal, but is due to pressure
from the cover glass or to some other unusual condition; in


such instances the cilia are like those in the normal stalked

2. Ciliary Movements. Add powdered carmine to the
water and observe the directions of the currents produced
and also the method of feeding. Watch the formation of
a food vacuole. If there is a movement of these in the body
indicate by arrows in a drawing the course taken.

3. Irritability. Notice what happens when the slide or
cover is tapped, and when the animal is touched by some-
thing. Is Vorticella more or less sensitive than Paramecium ?
Does it always contract when it touches something? Ex-

4. Reproduction. (a) Fission. Look for individuals un-
dergoing fission. Where does the division begin? In what
direction does the division take place? After the division
is completed one of the two new animals separates from the
stalk, swims away and later settles down, forming a new

(6) Conjugation. Individuals may rarely be found under-
going conjugation. In Vorticella this involves the per-
manent union and fusion of a small individual with one of
the normal stalked forms.

Questions on the Protozoa in General.

Tell something of the shape of protozoa, of their size. Is
the body symmetrical? Is the shape constant? Is there
any distinction of the animals into regions? What sorts
of motions have the animals? How are these movements
produced? Do all the protozoa examined have the same
motor apparatus? Does the body contain blood and is a
heart present? Is there anything corresponding to stomach,
lungs, or gills? Do the animals eat, digest food, breathe,


see, feel? Do they have nerves or brain? If the organs
needed for performing these functions in other animals are
absent in the protozoa, how can you account for the fact
that they do perform these functions?

Is the protoplasm protected in any way? What means
of defense have they? How can one account for their wide
distribution and abundance?

In what ways do these single celled animals differ from
the single cells of plants and of higher animals? In what
ways do they resemble each other? Could single cells from
the many-celled animals exist alone as do the Protozoa?

Write a brief paper answering the questions above and
discuss the points suggested.


PLEUROCOCCUS is a unicellular plant, growing on damp
stones or ground, and is very common upon the trunks of

I. Morphology.

1. General Structure. Note the appearance of Pleuro-
coccus in its natural growth on a piece of bark or damp wood.
Is it evenly distributed over the surface? Compare several
specimens of bark on this point. What is the color? Does
it vary in different specimens? Compare pieces of dry bark,
and those which have been in a moist place for several days.

2. Minute Structure. Scrape bits of the plant from the
bark and mount on a slide with water. Examine first
with the low power, arid then with the high power of the
microscope. Note the form of the cells, and whether they
are single or associated in definite groups. Make drawings
of any different appearances found.

Is there a cell wall? What is its color? Can the proto-
plasm be seen? The green color of the plant is due to the
presence of chlorophyll; usually this is distributed through-
out the protoplasm, though it may be in several distinct
chloroplasts or chlorophyll bodies. Is there any nucleus
which can be seen in the living cells?

n. Reproduction.

Look for cells which are in the process of division to form
groups of two, three, four or more cells. This is the ordinary


mode of propagation by Pleurococcus. Is there any regular
order in the number of cells produced ?

In some unicellular plants similar to Pleurococcus an-
other sort of reproduction occurs, viz., by a division within
the cell there are formed a number of motile cells called
zoospores. These may be of two sizes, the larger ones called
macrozobspores, and the smaller ones microzoospores. Lo-
comotion of these spores is by means of flagella. Can you
suggest any advantage in having a zoospore stage? A
conjugation of macrozoospores and microzoospores may


AMONG protozoa are to be found various species which,
instead of becoming independent and separating from their
fellows at once after division, remain for some time, or per-
manently, associated in colonies. The formation of groups
or companies was noted in Vorticella. Other vorticella-
like animals (Carchesium, Epistylis) may be grouped into
permanent, branching, tree-like masses. Gonium, Pandorina,
Volvox, are well-known examples of free-swimming colonies.
Such forms are especially interesting for they show the be-
ginning of differentiation and complexity in a phylum com-
prising the simplest organisms. They are further interesting,
(a) in suggesting a possible origin of multicellular organisms ;
(6) in that their animal or plant affinities are still open to

As a type of these colonial forms Volvox is suggested for
study. It may often be collected in the spring or fall from
small lakes or ponds containing Riccia, duck-weed and other
plants. By stocking jars from the water of ponds where
the organisms are found, and maintaining conditions as
nearly normal as possible, they may be kept in the labora-
tory for several weeks.

I. Morphology.

1. Form of Colony. -What is the general shape? Color?
If living, note the movements of the colony and determine
how it is produced. Of how many kinds of cells is the


colony composed? How do they differ in size, position,
and shape?

2. Structure. Note the size, shape, and large number of
cells which make up the body of the organism. How are
the cells connected with each other? Under high power
make out the flagella of the cells. How many has each cell?
With what part of the cell are they connected?

Make a careful drawing of a group of cells, their structure,
and connection to other cells.

n. Physiology.

1. Reproduction. (a) Asexual. Certain cells, partheno-
gonidia, migrate from the outer wall into the interior of the
sphere and there, without fertilization, give rise to small
colonies by repeated divisions.

(6) Sexual. Other cells which move into the interior of
the sphere are specialized reproductive cells. The egg
(macrogamete) is large, the spermatozoids (microgametes)
are small. These two kinds of cells fuse or conjugate and
the fertilized egg develops into a new colony.

Make drawings of different stages of reproduction, both
sexual and asexual.

Would you regard Volvox as a unicellular colony or as a
very simple multicellular organism? Give reasons for your



SPIROGYRA is a filamentous alga common in ponds,
ditches, or sluggish streams during the summer months,
usually floating on the surface or adhering lightly to some
support. It is often called "pond scum," "frog-spittle,"
"brook-silk." The scientific name comes from the spiral
arrangement of the chlorophyll in the cells. The alga may
be collected late in the fall and kept in aquaria all winter,
usually in good condition.

I. Morphology.

1. General Characters. Note the color, texture, slippery
feeling. Do different masses show variations in these
respects ? To what extent ?

2. Microscopic Characters. Mount a few filaments in
water and examine with low, and with high powers.

(a) Shape of Filament. Is it simple or branched? Is
it of uniform size? Are there signs of roots? Is there a
root end or a tip to the filament?

(6) Structure. Is the filament composed of cells? If
so are they of uniform size? Note any variations. How
are the cells united? Is a cell wall clearly distinguishable?
Is it of uniform thickness over all portions of the cell? Stain
the filament by running a drop of iodine under the cover
glass and note effects on all parts of the cell. Are there
indications of starch?


Mount fresh filaments and study the chlorophyll bands,
or chloroplasts. What is their general form? How many
in a cell? How many spirals of the chloroplast in a single
cell? Note the form of the margin of the band. What
relation has ;this to certain round bodies, the pyrenoids,
situated at regular intervals along the bands? Test for
starch in the pyrenoids and surrounding granules.

(c) Nucleus. Examine the cells in both fresh and stained
condition for the nucleus. Does it occupy the same position
in all cells ? What is its shape ?

Make drawings to show the points observed.

II. Physiology.

1. Plasmolysis. In fresh specimens look for a very deli-
cate film of protoplasm lining the cell wall. If it cannot
be found in fresh specimens try the following experiment of
plasmolyzing the cell: Run a few drops of a 10 per cent
solution of salt or sugar under the cover glass, and note
what happens to the protoplasm. Is there any change in
the cell wall? In the chloroplast? During the experiment,
and probably before, vacuoles will have been noted in the
cells. What effect had plasmolysis upon these? Explain.

2. Photosynthesis. Study the effects of light on starch
making by examining specimens which have been kept in
the dark for twenty-four hours and testing for starch. Com-
pare with specimens which have been freely exposed to light.
What conclusions may be drawn?

3. Reproduction. Occasionally during the summer or
fall Spirogyra may be found in the process of conjugation.
This consists in the union of cells of two parallel filaments
lying close together by outgrowths of tubular processes
from each cell, and their final fusion with those of the adjacent


cell. In this way there is a fusion of the protoplasm of the
two cells.

If filaments are found in this condition note any differences
in color and size of the filaments and cells, as compared with
the ordinary condition. Are all the cells of the filaments
undergoing conjugation in the same stages of conjugation?
Does the chloroplast take part in the process?

The result of this conjugation is the formation of a zygo-
spore. What is its shape? Color? Size? Are zygospores
found in cells of both the conjugating filaments? Is there
any indication of sexual distinction in the two filaments?
In what condition are the old cells after conjugation is com-



A FEW sponges are found in fresh water, but most are
marine; the latter are found in all parts of the world under a
great variety of conditions. Grantia is a solitary form,
not producing colonies as do many others, though buds at
its base may temporarily make a small colony. It is per-
manently attached to rocks, piles and sea-weed below low-
water mark.

I. External Anatomy.

Place a specimen in a watch glass in water or alcohol.
Observe the form of the animal, and its mode of attach-
ment. At the free end note the opening, the osculum,
partly covered and protected by a cluster of spicules. This
opening is not a mouth, but an excurrent opening for the
discharge of water from the animal. In the sides of the
animal are many minute openings, the incurrent pores or
ostia. Are these covered or protected by spicules like the

Make a drawing of a specimen.

II. Internal Anatomy.

With a razor cut a dry specimen longitudinally and ex-
amine the section with a lens. Observe the central cavity
and the small pores, the apopyles, which pierce its wall. In
the walls find a series of canals arranged in radial fashion.


These are of two sorts, incurrent canals open to the outside,
and radial canals or flagellated chambers which open into
the central cavity.
Draw the sectioned specimen.

III. Microscopic Sections.

Study stained sections made transversely through a
decalcified specimen. Make a careful study of the arrange-
ments of the parallel tubes in the walls, and their relation
to the central cavity. Are the tubes open at both ends?
Is it possible to distinguish the incurrent and the radial
canals? What structural features make this distinction
possible? Are there any openings, the prosopyles, between
the incurrent and radial canals?

With the highest power examine the cells. The central
cavity is lined by flat or pavement epithelium; the radial
canals are lined by peculiar cells, the gastral epithelium, or
choanocytes, which are elongated cells bearing flagella; the
incurrent canals and the outer surface of the body are cov-
ered with flattened cells, the dermal epithelium. Scattered
through the sections may be found germ cells, sperms or
eggs or segmenting eggs. Observe especially their location
with regard to the cellular layers.

Make a careful drawing of a portion of a transverse

IV. Skeleton.

If a specimen is boiled in caustic' potash the fleshy matter
will be destroyed, leaving only the skeleton. The latter is
made up of a series of spicules embedded in the flesh. Mount
some of these loose spicules in water and examine with
the microscope. Draw the different kinds found.


HYDRA is found in ponds and lakes which contain pond
weeds such as, Elodea, Sagittaria, water-lilies, duck weed,
and the like, usually being attached to these plants. Speci-
mens secured . from such localities and placed in aquaria
with aquatic plants will live indefinitely, if supplied with
food in the form of small Crustacea or "water-fleas."

From the aquaria in the laboratory remove hydra with
a clean pipette and place in a watch glass with water from
the aquarium. Place this dish on the stage of the dissecting
microscope and examine the specimens.

I. Morphology.

1. Form. Describe the shape and color of the animal.
Is the body differentiated into regions as head and base?
Is it attached or free? Do the length and breadth remain
constant? At the free end of the body is a row of tentacles,
how many are there? Is the number the same in all speci-
mens? Compare notes with other students to determine
this. If both the green and the brown hydra are available
compare them in number of tentacles. Are the tentacles
smooth and even in contour? Compare the length and the
shape of the tentacles when expanded and when contracted.
Within the circle of tentacles is a small opening, the mouth,
often difficult to see in living animals.

On the larger, mature, animals will often be found pro-
cesses resembling the hydra. These are young hydras, or


buds, and -this budding is the common method of repro-
duction. What become of the buds? Are colonies formed
by budding? Why?

Make an outline drawing of the animal in the expanded
condition, and one of the contracted animal.

2. Minute Structure. Place the dish containing the hydra
on the stage of the compound microscope and examine with
the low power; or place the hydra on a slide and cover with
a cover glass, supporting the latter to prevent crushing the
animal. Is there a cavity (the enteron or digestive cavity)
in the animal? Does the cavity extend into the tentacles?
Sometimes small particles may be seen floating in the cavity
of the body or tentacles, or even passing from the enteron
into the tentacles. From this fact what inference may be
drawn as to the structure of the tentacles and their mode
of nutrition?

Observe that the body is composed of layers (tissues),
an outer ectoderm and an inner entoderm. Which of these
layers is thicker? Are the layers made up of cells? In
which layer is the coloring matter located? Is the color
evenly diffused or is it segregated into distinct bodies?

Draw a portion of the body enlarged to show the layers;
also show the cells if it is possible to determine their outlines.

With the high power observe an extended tentacle. Do
you find ectoderm and entoderm? Are cells present? Note
the knobs on the tentacles, composed of oval, transparent,
bladder-like bodies or cells. These are the stinging cells
(nematocysts or thread cells) which represent modified
ectoderm cells. Where are the nematocysts most abundant?
Is there any definite arrangement of these cells? From
the outer end of each of these cells projects a stiff hair-like
process, the trigger or cnidocil. Within the capsule of the
cell is a coiled thread which may sometimes be made out


with the high power. The nematocysts may be discharged
from the body and the thread thrown out, this serving to
secure prey or to protect the animal. The capsule of the
cell contains a fluid which escapes through the thread, and
kills or paralyzes small animals. By gently tapping on
the cover glass above the animal, or by introducing beneath
the cover some irritating fluid as dilute acetic acid or iodine,
one may cause a discharge of the nematocysts. Study
such discharged cells and observe the capsule, the thread
and the barbs.

Drawings should be made to show the structures worked

H. Physiology.

1. Irritability. Touch various regions of the body with
a needle and note results. Is hydra sensitive? Are the
several parts equally sensitive? Jar the table or the slide.
What does the hydra do?

2. Contractility. Does the body of the animal show
spontaneous movements? Do the tentacles show the same
properties? Does the contraction of the tentacles and body,
or of all the tentacles, take place at the same time, or is
there independent movement and contraction? What
effects on the shape of the body do the various movements
produce? Do the movements seem to be definitely co-
ordinated or purposeful?

3. Locomotion. Does the animal remain fastened in one
place in the aquarium or does it move about? On the out-
side of the aquarium make a mark to locate the position of
an individual. Make several observations after some hours
or days and determine whether the specimen has moved.

4. Heliotropism, or movements in response to light. Ex-
amine hydra in the aquarium. Are specimens arranged


or distributed in any special relation to light? Note where
the specimens are most abundant, rotate the jar 90 to
180 degrees and observe again after several days. Have
the hydras retained the old position or are they in a new
part of the jar? Are they in the same position, relative
to the source of light, that they were before the jar was

5. Food Taking. It is possible to artificially feed specimens
by suspending bits of raw beef within reach of the tentacles,
or by placing it in watch glasses with hydra. The method
of capturing prey may often be observed by placing water-
fleas in a jar or watch glass containing hydra.

6. Reproduction. (a) Asexual. The presence of buds
has already been noted. How does the process take place?
In what ways does it differ from the process of fission in the
protozoa? What becomes of the bud? What parts of
the body are involved in the formation of the bud? Draw T .

(6) Sexual. The same individual usually produces both
male and female reproductive products. The spermaries
(testes or male organs) will be found, if present, as small
conical elevations on the body just below the tentacles.
If these are mature the microscope may show active move-
ments on the inside; this is caused by the swimming of the
spermatozoa within the testis. If the testis is ruptured the
spermatozoa may be seen swimming about in the water.
Is there more than a single testis on one animal?

The ovaries (egg-producing or female organs) usually
develop later than the testes and will therefore not be found
on the same animal that shows the male organs. The ovaries
are larger than the testes, more spherical, and occur near
the base of the animal. Within the ovary may sometimes
be seen the single large egg or ovum. Is there more than a
single ovary on one animal?


Which of the layers of the body is involved in the form-
ation of the reproductive organs? Make drawings.

III. Sections of the Body.

On the slides are thin sections of the body cut transversely,
that is at right angles to the long axis of the body. These
sections have been colored to render them more distinct.
Distinguish the ectoderm and entoderm. How are they
separated ? How does the supporting layer which separates
them differ from the ectoderm and entoderm? Is the
ectoderm of uniform thickness? Note shape, size and con-
tents of the cells. At the inner ends of the cells may some-
times be found muscular prolongations of the ectoderm
cells. Between the bases of the ectoderm cells are smaller
cells not extending to the surface. These are interstitial
cells and from them arise the nematocysts and the repro-
ductive cells.

Compare the cells of the entoderm with those of the
ectoderm in shape, size and contents. Look for gland cells
in the entoderm. These will appear as more deeply stain-
ing cells between the ends of the cells which border on the
enteron ; they secrete digestive enzymes.

Draw a portion of the section much enlarged showing,
especially, the cell structure.



PENNARIA is a colonial, marine animal growing on sea-
weed, on the piles of docks, and in similar places. It is
a relative of the fresh water polyp, which has already been

1. The Colony. Examine a portion of the colony with a
lens, and note that it consists of a stem with branches, each
terminated by a flask-shaped body. This body is called
the hydranth or zob'id, and represents a single individual of
the colony comparable to an entire hydra. Are all hydranths
alike in form and size? What is the general form and char-
acter of the colony? Is there any definite order to the
branching? How is the colony attached? This basal
portion, the hydrorhiza, is really a creeping portion of the
stem. Do young stems arise from it? In the stem the
central axis, which is the fleshy part of the animal, is called
the cosnosarc, and it is surrounded by a horny, dark colored,
protective sheath, the perisarc. Does the perisarc cover
all parts of the colony?

Make a drawing of the colony about twice natural size,
showing its habit of growth.

2. Hydranth. Place a portion of a colony in a watch
glass or on a slide and with the low power of the compound
microscope make out the form and shape of a single hydranth.
Are tentacles present? How many? How arranged? Are
the tentacles alike? If more than one kind is found note


the points of difference. A mouth is present at the tip of
the hydranth, but, unless open, will not readily be found.
Is there a cavity present as there was in hydra? Does it
extend into the stem and the tentacles?

Make an enlarged drawing of a single hydranth with a
portion of the adjacent stem.

With the high power examine the different tentacles of a
hydranth with care and make out the ectoderm and the
entoderm, and the boundaries of the cells. Are the tentacles
alike in the arrangement and relative size of the layers and
of the cells? Are they hollow as in Hydra? Look for
bladder-like, oval, transparent cells in the tentacles (the
nematocysts or stinging cells). Note their size and arrange-

Make drawings of portions of the different tentacles as
seen under the high power.

3. Reproduction. Reproduction in, Pennaria, and in the
hydroids generally, is of two kinds, asexual and sexual.

(a) Asexual. The entire colony is produced by budding.
Look for buds on the sides of the stem, just below the hy-
dranths. These buds produce new hydranths, and there-
by increase the size of the colony. Other buds are formed
on the sides of the hydranths, these are called medusae and
when they are full grown they separate from the hydranth
and float freely in the water. They have the power of
locomotion and swim about as distinct individuals. If
possible make out the structure of the larger ones.

(6) Sexual. The medusae formed by budding from the
sides of the hydranths are sexual individuals, and they pro-
duce either. eggs or spermatozoa. The eggs and the sper-
matozoa are ripe when the medusae are liberated, and are
cast into the water where fertilization occurs. The fertilized
egg develops into a free swimming larva which after a time


settles down, fastens itself to some body and grows into a

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Online LibraryCharles Wesley HargittOutlines of general biology ; an introductory laboratory manual → online text (page 4 of 10)