Charles Wesley Hargitt.

Outlines of general biology ; an introductory laboratory manual online

. (page 6 of 10)
Online LibraryCharles Wesley HargittOutlines of general biology ; an introductory laboratory manual → online text (page 6 of 10)
Font size
QR-code for this ebook

Scattered through the parenchyma are two large masses
and several smaller masses of brownish cells, the sclerenchyma.
Is there any definite arrangement to these masses? Com-
pare the shape and the grouping of the cells with that of
the parenchyma. Is it similar to the parenchyma? Is
the cell wall like that of the parenchyma cells? Is proto-
plasm present? Do these cells resemble more the paren-
chyma or the cortex? These cells are developed from the
parenchyma cells by the formation of lignin or wood, and
they serve to form a framework for rigidity and support.
Is the structure apparently adapted for this? Why would
the parenchyma not serve this purpose.

Make a drawing of the cells of this tissue.

Oval or circular patches are scattered through the rhizome
and are known as nbro-vascular bundles. These bundles
anastomose and form a sort of network through the rhizome
and frond, through which liquids are conducted from place
to place. Study one of the bundles carefully and make
out the following:

1. Bundle sheath, around the bundle.

2. Phloem sheath, parenchyma like cells containing proto-
plasm and starch.

3. Bast Fibers. Small cells with protoplasm.

4. Sieve Tubes. Large thin walled cells.


5. Tracheids. Very large thick walled, empty cells or

6. Spiral Vessels. Smaller empty cells.

The functions of the different portions of the bundles
must be determined by reference to text-books.

Make drawings showing the different cells of the bundles.

If possible examine longitudinal sections and identify
the tissues observed in the transverse sections.

In a very general way compare the organization and
structure of the fern with that of the earthworm or other
animal. Are there similar functions in the two, if so what
are they, and what organs perform them? What organ
system has the animal that is lacking in the plant and vice
versa? In what are the tissues alike, in what different? In
what respects are the cells of these tissues alike, in what

m. Reproduction.

Ferns present conspicuous sexual and asexual cycles, or
alternation of generations. Of these the ordinary fern plant
is the asexual generation or sporophyte, producing within
certain organs of the leaf numerous, non-sexual spores.
These germinating give rise to inconspicuous, sexual plants
forming the sexual generation or gametophyte, which form
the sex cells.

1. Sporophytic Organs. Examine mature leaves for the
spore-producing structures, sporangia, which are borne along
the margins of the leaflets. Observe the membrane, indusium,
which encloses and protects the sporangia. With needles
carefully dissect off the coverings and observe the sporangia.
Describe the shape, color and size of these capsules. Can
you find any variations? If so, how do you account for


Examine some of the sporangia, and work out the follow-
ing parts, using the high power where necessary:

(a) The Stalk or Pedicle. What is its shape and structure ?
(6) The Capsule which contains the spores. What is
its shape and structure? Note especially the annulus,
or crescent of thickened marginal cells forming a crest
or ridge. Is it continuous about the entire capsule?
Where is it most developed? Is the capsule more
fragile at one point than another? Examine several
capsules in demonstrating this point. Observe the
size, shape and arrangement of the lateral or parietal
cells of the capsule. i

(c) The Spores. Rupture sporangia by pressure of the
cover glass and examine the spores. What is their
color and shape?

Make drawings which illustrate the various struc-
tures studied above.

2. The Prothallium (Gametophyte). Study prothallia in
their normal growing condition if possible. What is their
general appearance, color and shape? Carefully isolate a
single specimen as directed by the instructor and proceed
to work out its distinctive morphological features. Is it
differentiated into an upper and a lower surface? If so,
what are the distinguishing characteristics? Has the plant
rootlike organs or rhizoids? \Vhere are they located and
what is then- probable function?

Carefully examine the lower surface of the prothallium
for the presence of the following organs:

(a) Antheridia. These are small somewhat spherical
bodies usually located among the bases of the rhizoids.
They correspond to the male sexual organs and may
contain small coiled antherozoids, the male sex cells.


(b) Archegonia. The archegonia, or female sex organs,
are small, finger-like projections in the region of the
sinus, or notch, of the prothallium. Compare care-
fully their shape and structure with that of the an-
theridia. When the archegonia are mature each
one contains a single egg cell.

Make drawings showing the location of the sex

organs on the prothallium, and also showing the

character of these organs as seen with higher power.

3. Development. After fertilization, which takes place

within the archegonium, the fertilized egg cell undergoes a

cleavage and gradually develops into a young fern. It soon

develops its own roots and leaves and becomes a perfectly

independent plant. The plant produced in this way is the

sporophyte generation.


DISSOLVE a small piece of compressed yeast in water,
mount a drop on a slide and examine with the compound
microscope. Or better mount a drop of Pasteur's solution
in which yeast is growing vigorously.

I. Morphology.

1. Form. What is the form of the yeast cells? Are all
cells of the same shape? Are they single or in groups?
Are the cells arranged similarly in different groups? Are
they uniform in size? Make drawings to show the points

2. Structure. Is a cell wall present? Note its color and
thickness. Is protoplasm present within the cell? Does
it show any color? Look for vacuoles within the cell. Is
more than one present? Is the size of all vacuoles the same?
Is there any difference in size or number of vacuoles in single
cells and in groups of cells? Is there any difference in size
and number of vacuoles in growing yeast and yeast from a
compressed cake. How can this be accounted for? Small
glistening oil drops are often present near the vacuoles. A
nucleus is present in each cell but it can be demonstrated
only by special methods.

H Physiology.

1. Reproduction. Examine cells from actively growing
yeast and from compressed yeast and note any differences


in form, number and size of cells in a group. Explain the

The chief method of reproduction in yeast is by asexual
budding or gemmation. How does this method differ from
fission in protozoa?

2. Growth. In the following experiments the amount
and rate of growth may be roughly estimated by the in-
crease in the turbidity of the liquids; fermentation may be
indicated by the rate and the amount of gas produced.

(a) Food Supply and Growth. Fill four test tubes (if
fermentation tubes are at hand better results will be
obtained by their use) half full of the following fluids,
and into each place the same amount of yeast from
the same culture. Keep all the tubes under the same
(I) Distilled water.
II) 10 per cent sugar solution.

(III) Pasteur's solution without sugar.

(IV) Pasteur's solution with sugar.

After several hours or a day observe the tubes and deter-
mine in which the growth and fermentation have been most
rapid and greatest.

(6) Other Conditions and Growth. Prepare several tubes
with Pasteur's solution containing sugar, and to each
add the same amount of yeast. Place some of the
tubes in a warm place (about 35 C) ; some in a cold
place (on ice if possible) ; boil some and place with
the first ones; to some add a few drops of a poison like
mercuric chloride or formalin; place some tubes in
the sunlight and others in darkness. Into a similar
tube place some yeast filtrate. After several hours,
or on the next day observe the tubes and note all the
differences. Draw what conclusions you can as to


the effect of the different conditions upon the growth
of yeast, and upon its power to cause fermentation,
(c) Fermentation. Conduct some of the gas being formed
in a culture of vigorously growing yeast through lime-
water or baryta-water. What is the effect on the
lime-water? A milky appearance or a white pre-
cipitate indicates the presence of carbon dioxide.
Is this the gas which is being produced by the yeast?
Permit yeast to grow in a large flask of Pasteur's
solution until growth has ceased, i. e., until gas is no
longer evolved. Distill the contents of the flask at
a low temperature (about 80 C) and test the dis-
tillate for alcohol by odor, taste, and inflammability.
(The test will be more certain if a second distilla-
tion is made.) What conclusions can you draw from
the experiment?

From the experiments upon the life and activities of
yeast write a report clearly showing the nature of the experi-
ments, the results, and the conclusions which may logically
be drawn from them. Give a summary of the conditions
which are favorable and those which are unfavorable for
growth and ferment action of yeast.


BACTERIA flourish only in the presence of moisture, but
are found in soil and air; indeed hardly any condition where
life is possible is devoid of bacteria. Some are among the
most useful and important of organisms, and others are
among the most dreaded and dangerous of all living things.
Many of the most virulent of diseases which afflict mankind
have been traced directly to bacteria. Some study of their
peculiarities, conditions of activity, method of protection
from them may be of interest and importance economically
and biologically.

I. Morphology.

Mount a drop of water from a hay or other infusion of
organic matter, or from slime in aquaria, and examine under
the highest power of the microscope. Note the numbers of
very minute, almost transparent bodies present, some in
motion and others quiescent.

The forms of bacteria are very simple and comprise only
three principal types: the sphere- (coccus), the rod (bacillus),
and the spiral (spirillum). How many of these kinds are
distinguishable in your preparation? Is the size variable?
Which type is generally largest, and which smallest? Is
the movement which is taking place a locomotion or merely
a vibration or oscillation?

Make drawings to show the shape and relative size of the
types of bacteria found.


II. Reproduction.

Bacteria reproduce chiefly by fission, hence the scientific
name of the order, Schizomycetes (Fission fungi). One
indication of this fission which may easily be observed is
the presence of chains or groups of bacteria. In what way
is this an evidence of division?

HI. Physiology.

Bacteria are plants but are not able to manufacture their
food as the green plants do. In order to grow they must
be in a medium which contains available food, and the
culture media used for their growth are so prepared as
to furnish the conditions necessary for their growth and

1. Distribution of Bacteria. Methods of preparing the
nutritive media can be found in any of the manuals on bacter-
iology. With tubes or Petri dishes containing sterilized
gelatin make the following experiments :

(a) Keep some carefully closed and labeled "not exposed."

(6) Expose some to the air of the laboratory for three
minutes, and label accordingly.

(c) Expose some to the dust from laboratory tables or
floor, or dust from the outside.

(d) Let a drop of water from the laboratory tap flow over

0) Capture a fly and let it walk over the gelatin.

Set these aside in a warm place and examine after a day
or two, noting what differences there are in the several
dishes. The small spots or patches probably present are
colonies of bacteria. Do they differ in form and color?
Examine the series still later. Have the colonies grown?


How is this indicated? Do any of the colonies have any
effect on the gelatin?

2. Surrounding Conditions and Growth. Into tubes of
bouillon introduce several drops of fluid from some culture
of bacteria and treat the tubes as follows :

(a) Close the tube with a plug of cotton.

(6) Close the tube with cotton and boil for five minutes.

(c) To a third tube add a small portion of a poisonous
substance, such as corrosive sublimate or formalin.

(d) Place some tubes in the bright sun and others in the
dark; place some on ice and others in a warm place.

Label all the tubes and set away for a day or more. Ob-
serve and note changes, if any, as indicated by the odor
and cloudy appearance of the culture fluid. Explain the



I. External Anatomy.

COMPARE with the earthworm with regard to regional
differences such as anterior and posterior ends, dorsal and
ventral sides, head and tail. Are these regions more or less
sharply marked? Is there perfect bilateral symmetry?

Distinguish an anterior region, the cephalothorax, and a
posterior, the abdomen. In what ways are they alike?
In what different? Is there a definite head? Note the
exoskeleton, is it present everywhere? Where is it thickest
and hardest, where thinnest? What explanation can you
give for these differences?

1. Abdomen. Is it segmented? If so, how many seg-
ments? The last segment is called the telson. Does it
differ from other segments? Is free movement of the seg-
ments possible? Is it equal in all directions? How are
the segments joined together? Are appendages present?
Are they present on all segments ? Are they alike ?

2. Cephalothorax. Is the form like that of the abdomen?
Are segments present? Is there any thing to suggest seg-
mentation? The shell-like exoskeleton in this region is
called the carapace. Are the edges of the carapace free or
fixed? To what extent? Are the appendages of this region
similar in form?

3. Sexes. Distinguish the following characters:


(a) Male. The first abdominal appendages are modified
into tube-like or spine-like organs; the abdomen is narrower
than the thorax; the genital openings are on the bases of
the hindmost legs.

(6) Female. The abdomen is slightly broader than the
cephalothorax; the genital ducts open on the bases of the
third pair of legs. What is the character of the first abdom-
inal appendages?

4. External Openings. (a) auditory, on the dorsal side
of the basal joint of the antennules; ('&) excretory, at the
base of the antennae on the ventral side; (c) mouth, on the
ventral side between the jaws; (d) genital ducts already
noted; (e) anus, on the ventral side of the last segment of
the body.

Draw the entire animal from the side, X 2.

II. Appendages.

1. Abdominal. Carefully dissect the appendages from
one side of the abdomen and arrange them in order on a
piece of paper. Using the third appendage as a type notice
its biramous character ; there is a basal portion, the pro-
topodite, and two distal portions, the exopodite and the
endopodite. Compare the other appendages with this one
and determine whether they have the same structure. Are
there any variations from this structure? What are they?
Which appendages show the greatest modification? In
what way? Can you explain it? Draw the first, the third
and the last appendage.

2. Cephalothoracic. In a similar manner dissect off the
walking appendages from the same side of the animal and
arrange them in order as before. Explain such differences
in structure as appear. Do these appendages bear any


resemblance to the third abdominal? Are protopodite,
exopodite and endopodite present?

Draw the first, the third and the last walking appendages.
The first pair are called chelae.

Remove the mouth parts on the same side, and arrange
them in order. From the outside inward they are called:
3d pair of maxillipeds, 2d pair of maxillipeds, 1st pair of
maxillipeds, 2d pair of maxillae, 1st pair of maxillae, mandibles.
Compare each one of these with the third abdominal ap-
pendage and with the walking appendages. Are they bira-
mous, are the protopodite, the exopodite, and the endopodite
present? Are the appendages of this group alike? Might
they be considered as modifications of a common structure?
Do they have the same number of joints as the walking
appendages? In the 2d maxilla note the gill bailer which
lies in the gill chamber and whose movement creates a
current of water which passes over the gills.

Draw the 3d maxilliped, the 2d maxilla, and the mandible.

Remove the antenna and the antennule from the same
side of the body. Compare with the other appendages,
what are the likenesses and the differences? Draw.

Considering all the appendages, indicate whether there
is a common plan in their structure, and if so what it is.
Also indicate what the departures from this plan have been,
and suggest advantages of these variations. Parts having
the same fundamental structure are said to be homologous;
and in this animal there is represented a serial homology.

HE. Internal Anatomy.

1. Respiratory System. Carefully cut away the carapace
from the side of the body and expose the gill chamber and
the gills contained therein. What is the form of the gills?


Of what advantage is this form? To what are the gills
fastened? How does the water get to the gills? Why are
they under the carapace?

2. Circulatory System. Carefully remove the carapace
from the dorsal side of the body. The heart will be found
in the posterior portion of the cephalothorax, as a delicate
shield-shaped body. Notice any vessels which extend out
from the heart and examine an injected specimen, if one is
available. Note the small openings in the heart, these are
valves. In what direction do they permit the blood to flow?
Trace all the bloodvessels which can be found.

3. Reproductive System. The ovaries are granular bodies
of considerable size located in the dorsal part of the thorax
and abdomen. Note the shape and extent of the organ
and trace the ducts to the openings already noted. The
testes are in a similar position but are smaller and are of a
whitish color; the sperm ducts are somewhat coiled and
longer than the oviducts.

4. Digestive System. Remove the gills from one side of
the body and cut away the body wall of the same side. This
will expose the greenish liver and the other digestive organs.
Remove .the lobe of liver on this side and expose the stomach
and intestine.

In the extreme anterior part of the body cavity will be
found the large stomach composed of two parts, from which
the intestine leads backward to the anus. Between the
mouth and the stomach there is a short esophagus. Trace
the digestive tube from the mouth to the anus, observing
the shape and the size of the parts and their exact position.
Do the large digestive glands, or livers, open into the intestine
or the stomach?

Draw the animal from the side as opened and show all
the organs that are exposed or that can be seen by dissection.


Open the stomach and observe the character of the lining.
Of what use are the teeth that are present in the walls ? How
do they operate? If food is present in the stomach try to
determine its character.

5. Excretory System. The openings have been noted
as being on the basal joint of the antenna?. The excretory
organs themselves, the kidneys or green glands, lie just
dorsal to the bases of these antenna? and therefore in the
extreme anterior part of the body cavity.

6. Nervous System. Dissect the muscle and other tissues
from the abdomen and expose the nerve cord. Be careful
not to break any of the nerves in cleaning away the muscle.
Expose the cord to the extreme posterior part of the abdo-
men, then trace it forward into the thorax, dissecting as
much as is necessary to expose it. In the anterior part of
the body the cord will be found to divide into two parts,
forming a commissure which passes around the esophagus
to the dorsal side. Here the two cords unite again to form
the cerebral ganglia or brain.

Notice the number, position, arrangement of the ganglia,
then* size, the distribution of the nerves which come from
them, and the termination of the nerves of the brain in the
sense organs of the head. Compare this nervous system
with that of the earthworm.

Make an enlarged drawing of the entire system.

IV. Physiology.

1. Locomotion. In working on the living animals do
not excite or irritate them. Place the crayfish in a pan
with sufficient water to cover it and observe it while walk-
ing_or crawling. What appendages are used? Can it walk
backward as well as forward? Are the legs used in any


definite order? Place the animal on the table, does it
walk equally well out of water? While the animal is in the
water frighten it by thrusting a pencil at it; notice how it
swims, what parts are used and how? What advantage
comes from swimming in this direction?

2. Defense. With a pencil make motions at an animal
to see how it defends itself. Allow it to grasp the pencil
to show the strength of the grasp.

3. Respiration. While the animal is at rest in the water
place a little colored liquid near the bases of the legs. Where
is this liquid drawn into the animal and where does it re-
appear? Try dropping the colored liquid at various places
along the edge of the carapace. What causes the movement
of the liquid? What purpose do the currents serve? How
is it that a crayfish, while breathing by gills, can live for
some time out of water?

4. Sensitiveness. Note the range of motion of the eyes.
Could an enemy approach the animal from any direction
without being seen? What are the advantages and what
the disadvantages of having the eyes on movable stalks?
In what ways are the eyes protected? Touch one of the
eyes and see what happens.

Test the sense of touch at various places on the body;
where is it most sensitive? Are all parts of the appendages
equally sensitive? Touch some of the hairs at different
places on the body; are they sensitive?

5. Feeding. Small pieces of meat may be placed near
the animal to determine how it reacts, and also to show in
what way the food is grasped and how it is passed to the
mouth. If possible note the action of the different mouth
parts. If this sort of a test is made you should also deter-
mine whether the animal prefers fresh or decaying meat.


THE following outline will apply to any of the common
grasshoppers, though the larger ones are, of course, pref-
erable for the study of the structure.

I. External Anatomy.

1. General Characters. The body of the grasshopper is
made up of head, thorax and abdomen. Are these divisions
well marked ? Are they as well differentiated as in the crayfish
and earthworm? Are somites present ? Are they found in all
regions of the body? Is an exoskeleton present? Compare
with the crayfish in regard to exoskeleton. In what ways
do they differ? Are appendages present? Are they found
in all regions of the body?

2. The Head. What is its shape? How is it attached
to the thorax? Study the position and structure of the
antennae. Observe the large compound eyes. With a lens
determine why these are called compound eyes. In addition
to these eyes there are three simple eyes or ocelli. One in
the center of the head, below the antenna?, and the others
near the dorsal, anterior border of the compound eyes.

About the mouth are several appendages: (a) labrum,
or upper lip; (6) mandibles, or jaws; (c) maxillae; (rf)
labium or lower lip. Observe the position each occupies
and the direction of movement. Remove the appendages,
note the structure of each one and make a drawing showing
this structure.


3. Thorax. Distinguish the Following divisions: (a)
prothorax, (6) mesothorax, (c ) metathorax. These three parts
of the thorax represent somites. Are they sharply separated
from each other? Do they move? In what respects do
they correspond to typical segments of the crayfish? Ob-
serve the several plates of which each is composed. What
appendages are borne by each somite?

4. Appendages of the Thorax. (a) Legs. How many?
Distinguish the following joints: coxa, a short segment
next to the body; trochanter, the second segment, which
may be fused with the first in the jumping legs; femur,
the middle segment; tibia; tarsus or foot. Is the tarsus
a single piece? Compare the several parts of each of the
legs with corresponding portions of the others. In what
are they alike ? In what different ?

(6) Wings. How many? On which somites are they

1 2 3 4 6 8 9 10

Online LibraryCharles Wesley HargittOutlines of general biology ; an introductory laboratory manual → online text (page 6 of 10)