Emanuel Roth Boyer.

A laboratory manual in elementary biology; an inductive study in animal and plant morphology designed for preparatory and high schools online

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(0) What do you suppose is the function of the first and
second pairs of legs? The third pair? What
methods of locomotion has the Grasshopper ?

D. — THE ABDOMEN AND ITS PARTS.

(a) Observe the general shape of the abdomen, and the
shape and arrangement of its somites. Does the
covering of each somite extend entirely around the
body as one piece ?

(6) Examine the broad triangular piece in the dorsal region
next to the metathorax. This represents the first ab-
dominal somite. Does it extend entirely around the
body?

{c) In the side of this incomplete somite observe (m)
a large crescent -shaped cavity (auditory sac) contain-
ing across its opening a delicate shiny membrane
(tympanum), ear drum. Near the anterior edge of
the auditory sac, observe (m) a spiracle.

(a) Examine the covering or exoskeleton of the second ab-
dominal somite. Of how many pieces does it consist ?
Identify the tergite, pleurite and sternite as you did in
your study of the Crayfish.

(e) How many abdominal somites has this Grasshopper?
Carefully c6unt the tergites, beginning with the first or
incomplete somite. Now count the sternites.

(/) Along the ventral edge of the pleurites observe (m) a
series of spiracles. In which somites do you find
spiracles ?



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THE GRASSHOPPER. 39

(g) Observe that the somites in the posterior region of the
abdomen are much modified in shape. This modifi-
cation varies with the sex. In the female the abdomen
is more tapering than in the male, and ends in two
pairs of curved spines (ovipositor) which when brought
together form a channel through which the eggs are
deposited into the ground. Of which sex is your
Grasshopper?

{h) Make a careful sketch of the abdomen, left view, repre-
senting all your observations (X 3).

(/) What are the principal points of similarity and difference
between the Crayfish and Grasshopper ?

INTERNAL ANA TOMY.
E. — CIRCULATORY AND REPRODUCTIVE ORGANS.

(a) Take a large Grasshopper, either alcoholic or fresh, and
remove the wings. Pin the specimen dorsal surface
up, on the bottom of the dissecting tray. Remove
the dorsal portion of the exoskeleton by begin-
ning with the eighth or ninth somite and carefully
cutting through the hard covering forward along the
left side of the body to the head, using sharp pointed
scissors. Now return to the point of beginning and
with your forceps lift the cut edge of the upper wall,
and with the point of your scalpel carefully loosen the
tissues attached to its inner surface, turn the flap
to your right and pin it down. The organs should
should be studied under water.

(B) Examine the heart, which is a dorsal tube similar in posi-
tion to that of the Crayfish. How does it differ from
the heart in the latter animal ? Sketch.

(c) Observe (m) the row of white rounded bodies (air-sacs)
along each side of the abdomen. The air-sacs are



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40 ANIMAL TYPES.

likely to remain attached to the inner surface of the
flap which has been turned back. Note the white
branched tubes (tracheae) connected with the air-sacs.
How are the air-sacs and tracheae related to the spiracles?
Carefully remove an air-sac and a portion of a trachea
and examine them under the microscope {lp). Sketch.

{d) If your specimen is a female, identify* the ovaries
which are likely to be quite prominent in the abdom-
inal cavity. Note the shape (m or lp) and color of the
ova. Sketch (x 4). Identify the oviducts, one on
each side, leading to the ovipositor.

(e) Remove all the eggs on the left side, being careful not
to injure the organs which lie below.

(/) In the lateral regions of the thorax observe the large
white bundles of muscles. Note their direction on the
the right side. What do you suppose is their func-
tion? .With your forceps pull off a small bit of muscle,
tease it out on a slide with your needles, and
examine it under the microscope {lp). Sketch.

(g) Examine (hp) a permanent preparation of stained muscle.
Note the fine thread-like structures (muscle fibres).
Observe the more highly stained nuclei. Carefully
focus upon a fibre and determine whether there are
faint parallel markings across it (striated muscle fibre),
or whether the fibre is without such strice, or marks
(unstriated muscle fibre). Make a careful sketch repre-
senting a few fibres with nuclei, etc.

F. — THE DIGESTIVE ORGANS.

(a) Clear away ail the muscles in the thorax lying above or

along the left side of the alimentary canal.

(b) Trace the digestive tube or alimentary canal, beginning

at the anterior end. Observe the dark portion of the
tube, (esophagus, passing up from the mouth and

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THE GRASSHOPPER. 4 1

curving backward. Note its enlargement (crop) in the
prothorax.

(c) Back of the crop, note several spindle-shaped pouches

(gastric caeca) which extend parallel with the digestive
tube. Are the gastric caeca connected with the digest-
ive tube ? How many are there ? Make an outline
sketch of the digestive tube up to this point (X3) and
develop it as you continue your study.

(d) Back of the gastric caeca, observe an enlargement, the

true stomach. Through how many abdominal somites
does it extend?

(e) Trace the intestine from the stomach to its external open-

ing. Complete your sketch.
(/) Press the crop a little to the right and look for several
clusters of small bodies (salivary glands) and note the
small tube which connects them with the mouth. Sketch

(X3).
(g) Write up your notes on the anatomy of the Grasshopper,
and make careful drawings of the principal organs.

OTHER WORK.

1. The morphology and physiology of respiration and cir-

culation in the Grasshopper.

2. Comparative review of the digestive and nervous systems

in the Grasshopper and Crayfish.

3. The general characteristics of the Moth, Beetle, Bee,

Fly, etc.

4. The characteristics of Spiders.

5. The life-history and metamorphosis in insects.

6. Intelligence in insects and lower types of animals.

7. The relation of insects to plants, and their injurious and

beneficial relations to man.

8. The characteristics and the orders of Insecta.

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STUDY VIII.
A STUDY OF A FRESH-WATER MUSSEL.

UNIO PL/CATA.

As an example of the soft-bodied un segmented Mollusk type.

♦Material Required. — (i) living mussels; (2) stock supply for dissec-
tion ; (3) a set of transverse sections for gross anatomy ; (4) a supply of
shells ; (5) a few injected specimens ; (6) the young stages of the mussels ;
(7) microscopic preparations of tissues.

Habitat.

The Pond, or Swan Mussel is common in ponds, slow
streams, and canals. It prefers a muddy or sandy bottom
where it can sink until only the extreme posterior dorsal edge
is exposed above the mud and sand. It is easily kept in the
laboratory throughout the year. For observation and study
the live Mussel should be kept in an aquarium containing
several inches of clean sand in the bottom. A stock supply
of live Mussels may be kept in a tub or tank and if the water
is changed once or twice per week they will not suffer for the
want of a constant flow of fresh water.

The Mussels intended for gross sectioning should be killed
in an aqueous solution of 0.25 per cent, chromic acid in which
they remain about forty-eight hours, and are then transferred
to alcohol. Mussels intended for dissection may be killed
by being put into cold water and slowly warmed to a tempera-
ture of about 70 C.

♦Any species of Unio, Anodonta, or even the Quahog, will answer very well for this
study.

42



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THE FRESH-WATER MUSSEL. 43

LABORATORY WORK.

EXTERNAL MORPHOLOGY,
A. — THE TOPOGRAPHY AND GENERAL FORM OF THE SHELL.

(a) Observe the general shape of the shell. Note that one

end anterior is more blunt than the other posterior
end, and that one edge (dorsal margin) is thicker than
the opposite (ventral margin). With trie anterior end
pointing away from you and the dorsal edge upward,
sketch the outline of the dorsal edge and name the ends.

(b) Of how many pieces (valves) is the shell of the Mussel

composed ? How can you designate the valves with
reference to the animal ?

(c) Determine which is the right and which the left valve.

Make an outline sketch of the right valve and indicate
the anterior, posterior, dorsal and ventral regions.

B. — THE OUTER SURFACE OF THE» SHELL.

(a) At the dorsal margin observe a pair of elevations
(umbones, or beak), one on each valve. Is the umbo
nearer the anterior or posterior end ?

(6) Between the umbones and extending back of them note
a smooth band (hinge-ligament). How is the ligament
related to the valve ? What function do you attribute
to the ligament ?

(c) Note the markings (lines of growth) on the surface of the

valves. Describe their origin and direction. What is
the nature of these lines, and how do you suppose
they are formed? Do you find any other surface
markings? Describe them. Sketch the left valve
and represent the umbo, lines of growth, etc.

(d) Observe the thin, horny membrane (periostracum) pro-

jecting along the ventral edges of the valves (m).
Do you find the periostracum in any other region (m)?



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44 ANIMAL TYPES.

(e) Note and describe the coloring of the valve. Make an
outline drawing of the dorsal aspect.

C. — THE INNER SURFACE OF THE SHELL.

(a) *Place a Mussel in water sufficient to cover it and slowly

warm to about 40 C. Raise the left valve, and be-
ginning at the ventral edge, with the handle of your
scalpel carefully free the membrane attached to the
inner surface of the valve. Now cut through the
tough bodies which are attached to the valves, one
near the anterior and one near the posterior end of
the shell.

(b) Note the character of the inner surface of the shell.

Observe its texture and color.

(c) Note the form and structure of the hinge ligament.

Press the valves together and then release them and
note the result. What is the function of the hinge
ligament ? Examine its structure carefully to deter-
mine how it performs its function.

(d) In the anterior region of the dorsal edge of the right

valve note an irregular projection (hinge "tooth"),
and a little distance back of this structure note another
of very different form. Can you find a mate for each
of these structures on the left valve ?

(d) Compare the anterior tooth (cardinal tooth) with the one

farther back (lateral tooth). How do they differ? Are
the mates of the cardinal teeth alike? Are those
of the lateral teeth alike ?

(e) What function do you attribute to the hinge teeth?

Why? Sketch each pair.
(/) Near the anterior end of the valve, note a scar-like struc-

*In order to economize the time of the class, the instructor should prepare the Mussels
in advance.



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THE FRESH-WATER MUSSEL. 45

ture (anterior adductor impression) where a large muscle
has been attached, and a similar one near the poste-
rior end of the valve (posterior adductor impression).

(g) In each muscle scar observe (m) the circular markings
(lines of growth). Sketch a muscle scar and show these
lines.

(h) A short distance from the ventral edge and extending
parallel with it, note a boundary line (pallial line).
Where are the ends of this line? Sketch.

i

D. — THE STRUCTURE AND COMPOSITION OF THE SHELL.

(a) Take a piece of shell and examine (m) the broken edge.

How many kinds of layers can you distinguish?

(b) Is the structure in each layer the same? Compare the

relative thickness of the layers. Sketch the broken
edge.

(c) Put a small bit 4 of shell into a test-tube and add a few

drops of acid (at the sink.) Note the result. What do
you infer?

(d) Examine a shell which has been exposed to great heat.

1. e., burnt. What do you observe?

E. — EXTERNAL APPEARANCE OF THE BODY IN OPENED SHELL.

(a) In a specimen with the left valve removed, note the gen-

eral appearance of the body. Note the character ot
the body-wall. Identify it in the different regions.
Which side of the body is exposed?

(b) Note the whitish circular structures, one near the anterior

(anterior adductor muscle) and the other (posterior
adductor muscle) near the posterior end of the body.
What corresponding structure did you find in the
valves?

(c) What relation between these muscles and the muscle



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%6 ANIMAL TYPES.

scars do you infer? What function do you attribute
to the adductor muscles?

(d) Note the flap of membrane (left mantle-lobe) which cov-

ers the left side of the body. With your forceps
gently lift it by its ventral edge and trace and describe
its free edge. Sketch the outline of the mantle and
indicate the position of adductor muscles.

(e) Note the right mantle-lobe. Is it anywhere attached to

the left lobe? If so, where?
(/) Lift the edge of the right mantle and note the line of

attachment to the shell. What is this boundary line?
(g) At the posterior end of the mantle note the fringed

edges (siphons) of the mantle. How are the two

mantles related in this region? Examine (m) the dark

tips (tentacular processes) on the siphons. Sketch the

siphons, representing the processes.
(h) With your forceps lift the left lobe and note the space

(pallial, or mantle cavity) between it and the right lobe.
(*) Note how far dorsally the mantle is free from the body,

or the extent of the pallial cavity.

F. — THE ORGANS LYING IN THE PALLIAL CAVITY.

(a) With your scissors carefully trim away the mantle along
its line of attachment to the body, beginning at the
anterior adductor muscle. Make a sketch locating the
muscles and representing the course and position of
the cut edge of the mantle. This cut edge represents
the dorsal boundary of the pallial cavity.

(6) Note the membranous structures (gills) which are
attached to the body along the dorsal Tegion of the
pallial cavity.

(c) Play a stream of water from your pipette upon the gills
and cause them to float and separate so that you may



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THE FRESH-WATER MUSSEL. 47

observe their exact form and relation. Observe their
attachment and relation to the body. How can you des-
ignate them ?

(d) With your forceps carefully lift the upper (left outer gill)

and observe and note its size and shape ? Which
edge is attached and which edges are free ?

(e) Lay the outer gill back and lift the lower (left inner gill)

and note its size and shape. How are the two gills
related? Now lay them into their natural position.
Which is the larger, and in what directions ? Make
an outline sketch of them in their natural position.

(/) Examine (m) the surface of the outer gill and sketch a
portion of it. Examine {lp) a microscopic prepara-
tion of cross sections of the gill. Sketch.

(g) Near the anterior adductor, observe (m) a pair of small
membranes (labial palpi, or palps). Move them
slightly with your forceps, or play the pipette upon
them and note their position, shape, and relation.
Designate the palps as you did the gills.

{h) At the anterior end, how is each palp related to its mate
oh the other side of the body ?

(1) Between the outer and inner palps, at their extreme
anterior ends, search (m) for a small opening (the
mouth). Insert bristle. What do you suppose is the
function of the palps ? Sketch the palps and indicate
the position of the mouth.

(J) Observe the large firm structure (foot) lying below the
left gills and palps. Note its shape and sketch its
outline. Name the organs which you have thus far
observed in the pal Hal cavity.

{k) Note that the part of the pallial cavity which extends
from the base of the gills ventrally (branchial
chamber) is more or less separated by the gills and



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48 ANIMAL TYPES.

foot into several compartments. How many com-
partments in the region of the foot ? How many
back of the foot ?

(/) Observe that at the posterior end of the gills the right
and left mantle lobes meet and form a longitudinal
partition through the siphon region. This partition
thus forms an upper space or tube (exhalent, or cloacal
siphon) and a lower (inhalent, or branchial siphon).
(m) Which siphon connects with the branchial chamber?
Which connects with the cloacal chamber ?

(«) In the cloacal siphon just back of the posterior adduc-
tor, note a small opening (anus).

(o) Make careful drawings of the different views of the
valves and of the Mussel lying in the shell. Write a
description of the Mussel as far as now studied.

•INTERNAL ANATOMY.
G. — THE CIRCULATORY SYSTEM.

(a) In the dorsal region of the body, between the hinge
ligament and the base of the gills, observe the outline
of a longitudinal cavity (pericardial cavity) protected
only by a delicate portion of the body wail. With
your scissors carefully cut away this delicate membrane
as far as the anterior ends of the gills and back to the
posterior adductor muscle. This somewhat triangular
opening exposes the pericardial cavity.

(6) In the central region of the pericardial cavity, observe
the pale muscular heart consisting of three divisions
of which two are readily seen. Examine first the
elongated thick-walled sac (ventricle) lying in the

* The student should be impressed with the fact that although a valve or exoskeleton of
the animal has been removed, yet his study up to this point has been external to the true body



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THE FRESH-WATER MUSSEL. 49

middle of the cavity. Note that it is somewhat coni-
cal, its smaller end extending forward and the larger
bi-lobed end backward.

(c) Now observe a thin-walled, triangular sac (left auricle) hav-
ing its apex connected with the lateral region of the
ventricle and its base extending along the base of the
gills. By carefully lifting the ventricle, a portion of a
similar structure (right auricle) may be seen on the
opposite side of the body. The auricles receive
aerated blood from the gills and convey it to the ven-
tricle, which in turn by its contraction sends the blood
to all parts of the system.

(d) Trace the anterior end of the heart forward and observe
that it gradually becomes a firm-walled tube (anterior
aorta) which lies along the side of a larger tube (intes-
tine). The anterior aorta conveys aerated blood from
the ventricle to the "foot," viscera and the anterior
region of the body. At the posterior end of the ven-
tricle observe a similar blood vessel (posterior aorta)
which divides into right and left branches. This
vessel supplies aerated blood to the posterior regions
of the body. * Make a careful sketch of the pericar-
dial cavity, showing the heart, aortas and intestine.

(<r) Examine blood corpuscles, either fresh, which may be
taken from the auricle by means of a pipette, or in a
permanent preparation. Note the form and size and
color of the corpuscles. Sketch.

H. — THE ALIMENTARY CANAL.

(a) Beginning at the mouth, determine the course and
regions of the alimentary canal. Insert a seeker into

* The student should have an opportunity to see the pulsations of the heart in a live Mus-
sel. For this demonstration the valve should be removed as described in the foregoing direc-
rections (p. 44) and the animal kept under water.



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50 ANIMAL TYPES.

the mouth and pass it in a dorsal direction as far as it
will easily go. Now with your scissors sHt open this
region of the alimentary canal, oesophagus, and note
its position and length.

(d) Note the enlargement, stomach, at the inner end of

the oesophagus. Carefully examine the shape and size
of the stomach. Along its ventral wall, seek a small
opening which leads obliquely down and backward
into another portion of the alimentary canal, intes-
tine. Use the seeker to guide you in the direction
of the intestine. Now slit open this portion of the
intestine. Make a sketch of the alimentary canal
from the mouth to this point, and develop it as you
proceed to reveal the direction and position of the
remaining portions of the canal.

(e) Observe a lobed gland, liver, surrounding the stomach

and a portion of the oesophagus. Represent the liver
in your sketch.
(d) Carefully trace the intestine to its entrance into the
anterior end of the pericardial cavity which begins
just back of the stomach. Note whether the diam-
eter of the tube or the thickness of its wall has varied.
(e) Trace the remaining portion of the alimentary canal
(rectum) horizontally through the pericardial cavity,
and observe that it seems to enter the anterior region
of the ventricle. Carefully dissect away the ventricle,
which really passes around the sides and over the
rectum. Bring up your sketch to this point.
(/) Trace the rectum from the posterior end of the peri-
cardial cavity, and observe that it passes along over
the dorsal region of the posterior adductor muscle,
and then obliquely downward, and opens through a
§mall slit, anus, into the cloacal chamber.



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THE FRESH-WATER MUSSEL. 5 1

(g) Examine a transverse section through the body of the
Mussel in the region of the "foot" and identify all
the structures which you have now learned. Make a
careful sketch of this section.

{h) Examine {lp) preparations of the young stages, or larva
(glochidia) of the Mussel. Sketch.

(/) Write a careful description of the anatomy of the
Mussel from your notes and sketches, and make
drawings of . the alimentary canal and circulatory
system.

OTHER WORK.

1. General view of the morphology and physiology of the

Mussel.

2. The significance of the absence of appendages and the

unsegmented body in the Mussel.

3. The life -history and habits of the Mussel.

4. The general characteristics of the Oyster, Snail, Squid,

Cuttlefish and Nautilus with comparisons.

5. The characteristics of Bryozoa and the Ascidia.

6. Oyster culture and the economic interests in the Mol-

lusca.

7. Characteristics and the classes of Mollusca.

COMPARATIVE REVIEW ON THE MORPHOLOGY OF THE INVERTE-
BRATE TYPES.

It is important at this point that the student should take a
thorough review on the invertebrate types, and that this
should embrace not only his laboratory work upon these types
but also his lectures and collateral reading included under the
head of Other Work.

1. Comparative review of the general external appearance

and the habits of the invertebrate types of animals.

2. The hard parts or exoskeletons, — spicules, spines and



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52 ANIMAL TYPES.

ossicles, setae, chitinous shells and bristles, calcareous
shells.

3. The organs of digestion and assimilation, forms of pre-

hension, digestion in the simple cell, in the special-
ized cell, the enteron or primitive alimentary canal,
the true alimentary canal, the more highly specialized
alimentary canal, the glands aiding in the process of
digestion.

4. The organs of respiration, — by means of general sur-

face; specialized regions; tracheae; gills.

5. The organs of circulation, — in the simple cell; in an

aggregation of simple cells ; true blood vessels, a heart
and arteries ; lacunae and veins ; true capillaries and
a closed system; the simple "arterial heart."

6. The muscular system; — contractility as a characteristic

property of protoplasm ; specialized muscle processes ;
muscle fibres ; muscles and a complex system.

7. The sense organs; — sensation in the animalcule; spe-

cialized nerve fibres; nerves and ganglia; specialized
nerve centres ; organs of sight ; organs of hearing.

8. Reproduction; — simple cell division ; budding; special-

ization of two kinds of cells in the same animal;
gonads, distinct sexes. The course of development
from the ovum.

9. A general view of the gradual advance from the simple

to the complex in structure, and from the simple to
the highly specialized in function.



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STUDY IX.
A STUDY OF A RIVER PERCH.

PERCA FLAVESCENS*
As an example of the simpler vertebrated type, having a true internal skeleton.

Material Required. — (i) Live minnows or any small fish in an aqua-
rium ; (2) a supply of fresh Perch "f ; (3) a dissection showing the digestive
and circulatory systems ; (4) a dissection of the central nervous system; (5)
a mounted endo-skeleton of the Perch ; (6) a supply of disarticulated bones ;
(7) microscopical preparations of tissues; (8) preparations showing the
principal stages in the development of the egg.

Habitat.
The Common Perch inhabits the streams and lakes gener-
ally throughout the northern regions of the United States.
It is an important food-fish, and may be obtained from the


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Online LibraryEmanuel Roth BoyerA laboratory manual in elementary biology; an inductive study in animal and plant morphology designed for preparatory and high schools → online text (page 4 of 15)