c. Drawings to show that paramecia are constant in shape and yet

flexible.

d. A drawing to show at least one stage in fission. This may be from a permanent preparation.

e. A drawing to show paramecia conjugating. This also may be from a permanent preparation.

f. Instead of all these separate drawings they may be combined into one. Represent the field of the microscope, and in it draw all necessary figures, to show the facts called for in the first five drawings and any other facts you have observed about living protozoa. Make the whole drawing to scale.

Summary of Important Points in the Study of Paramecia

1. Look back over your study of paramecia and list the different kinds of work you saw paramecia doing; also the kinds of work you infer they can do. What organs have they to use? When there is no organ to do a given thing, _e.g._ to digest food, how is the work done?

2. What conditions are favorable to paramecia? Why are they so numerous under favorable conditions?

3. What would you call a successful animal? Are paramecia successful? Give reasons why they are or are not.

Comparative Study of Protozoa

To enlarge your idea of what a cell can do, spend as much more time on the one-celled animals as your course will permit. Any stagnant water may furnish several kinds. By means of reference books, identify as many as you can. In each case notice:--

1. Its size, shape and general appearance, comparing and contrasting it with paramecium.

2. Its usual surroundings, _i.e._ the conditions it has to meet.

3. The means it has of finding out facts about its surroundings.

4. The means it has of adjusting itself to its surroundings. For example, is it stationary? If so, what does it do when conditions change? Is it locomotory? If so, how effective is its locomotion?

5. What is its food? How does it find food?

6. Can it do as many kinds of work as paramecium can? Can it do any that paramecium cannot do? If so, what?

Review and Library Questions on Protozoa

1. What are the characteristics which distinguish protozoa from other animals?

2. What are the classes of protozoa? Characteristics of each class?

3. What is digestion? Where does it take place in the protozoa?

4. What results from the fact that the amoeba has no cell wall? (Give at least two points.)

5. In what ways are paramecia more specialized than amoeba are? How does their greater specialization show in their work?

6. What different methods of locomotion are shown among protozoa? By what means is locomotion accomplished in each case?

7. What is encysting? Name some protozoa which encyst. How long may an encysted animal live? When do they encyst? Why?

8. Give methods of reproduction among protozoa. Which method is fitted for rapid multiplication, for withstanding drouth; for renewing vitality?

9. Many scientists speak of protozoa as immortal. What argument is there to support such a statement?

10. Why are no protozoa large animals? Give at least two reasons.

11. Why are protozoa so numerous? Why more numerous in stagnant water?

12. Where are protozoa found?

13. Why are protozoa so widely distributed?

14. Write the probable history of a piece of chalk.

15. What connection is there between protozoa and some polishing powders?

16. Where in the human body are malarial protozoa found? How are they transferred from one human being to another? Why is there likely to be more malaria in newly settled regions than in older ones? If you were obliged to spend some time in a region where malaria existed, what precautions would you take?

17. Name other diseases caused by protozoa. How are they fought?

18. What beneficial effect have some protozoa upon the water of stagnant ponds and ditches? How may some forms injure water for household purposes?

19. Give at least three reasons for thinking that protozoa are the most ancient animals.

20. Why are protozoa of great importance to the world?

2. A STUDY OF SPONGES

_To show how cells loosely associated may work together_.

_Materials._

The simplest of the many-celled animals are the sponges, which, with one exception, are salt-water forms. That one, the spongilla, is not easily found and is very difficult to maintain in the laboratory. For these reasons the material for this study is very meager, except at the seashore, and much of the work must be done from diagrams and reference books. Small simple preserved sponges and complex toilet sponge skeletons will also be used.

_Definitions._

_Body wall_, the outer wall in bodies of the many-celled animals.

_Central cavity_, the cavity surrounded by the body wall in the simpler many-celled animals, as in the sponges.

_Canals_, channels through the body walls of sponges.

_Inhalent pores_, the outer ends of the canals.

_Ostia_, the inner ends of the canals.

_Osculum_, the large opening of the central cavity, at the distal end of the sponge.

_Spicules_, tiny needles of mineral substance found in the walls of many sponges.

_Fibers_, flexible threads of horny material found in the walls of many sponges.

_Endoderm cells_, cells lining the canals. They have cilia or flagella (projections larger than cilia).

_Ectoderm cells_, cells covering the outside of sponges and some other animals. In sponges it is believed that endoderm and ectoderm cells are able to exchange positions and functions.

_Mesoglea_, a jelly-like layer between the endoderm and ectoderm layers. In the sponges this contains many wandering cells, probably from the other layers.

_Porifera_ (pore bearers), animals with many more or less independent cells, supported by solid skeletal parts and penetrated by a system of canals which open on the surface as pores.

_Directions._

Study a simple sponge to see the shape, size, and point of attachment. Identify the osculum. In a diagram of a long section of a simple sponge identify the central cavity, body walls, canals, inhalent pores, ostia, and osculum. In a simple sponge cut like the diagram identify the same structures. Do the same for the toilet sponge.

Study a diagram of a portion of the body wall, considerably enlarged. Identify the endoderm and ectoderm cells, the spicules or fibers, and, among the spicules or fibers, irregular amoeboid cells, sometimes called mesoderm cells.

Examine a fragment or section of each kind of sponge under the microscope. Notice the arrangement, shape, and length of the spicules and of the fibers.

Test both kinds of sponges by dropping a bit of each into weak acid, and noting the results. Also burn a bit of each and notice the odor.

_Questions._

1. What is the shape of a simple sponge? What enables a mass of cells to retain such a definite shape?

2. What seems to be the composition of the skeletons? Why is one type of skeleton rigid and the other elastic?

3. Since sponges are attached for most of their lives to stationary objects, suggest means for obtaining food and oxygen, and for getting rid of waste matter.

4. Although individual cells are sensitive, a sponge as a whole is not. What connection has this fact with the fact that sponges are stationary?

5. Compare simple and complex sponges.

_Suggested drawings._

a. A view of a simple sponge. Label everything shown.

b. A diagram of a simple sponge split in halves. Show by arrows the path followed by the water as it passes through the sponge.

c. A few spicules.

d. A few fibers.

Summary of Important Points in the Study of Sponges

1. What are two functions of the spicules or fibers?

2. What are at least two of the functions of the endoderm cells?

3. What can you suggest as functions for the ectoderm cells?

4. In what cases do cells show "team work" in accomplishing an object?

5. What degree of specialization is indicated by the fact that the cells may exchange positions and functions?

6. What work can any single cell of a sponge do? Compare the work done by such a cell with that done by a paramecium.

7. What work can a whole sponge do? Compare that with the work done by a paramecium.

Review and Library Exercise on Sponges

1. What are the distinguishing characteristics of Porifera?

2. Sponges were once supposed to be plants. In what respect are they plant-like? What made students finally class them as animals?

3. How do sponges reproduce? How are they distributed to new locations?

4. Where, as to depth of water, do most sponges grow? Where, as to oceans? Where, as to latitude?

5. What are some of the difficulties which confront a stationary animal? How are they overcome?

6. To what class of sponges do the "toilet" sponges belong? Why?

7. What conditions are necessary for toilet sponges to thrive? Where are the best ones found? Where are they most numerous? How are they collected? How are they prepared for market?

8. What is man able to do toward raising good sponges for market?

9. Using reference books and museum specimens, describe some especially odd sponges.

3. A STUDY OF COELENTERATES

_To show cells working together more definitely than in Sponges_

A Study of Hydra

_Materials._

Living hydras in permanent aquaria, undisturbed. Living hydras in small aquaria, _i.e._ tumblers, test tubes, watch glasses, etc., with pieces of water weed and if possible some of the microscopic animals found in water where hydras are abundant. If kept cool, hydras may live several days in such aquaria. Permanent slides of hydras; some whole, some in sections, and some showing the organs of reproduction.

_Definitions._

_Proximal end_, the end by which an animal is attached to an object.

_Distal end_, the end opposite the proximal end.

_Tentacles_, slender projections around the distal end.

_Mouth_, the opening through the distal end, into the central cavity.

_Bud_, a small hydra or other coelenterate growing out from the wall of the parent.

_Mesoglea_, a thin, gluey partition, without wandering cells, between the ectoderm and the endoderm.

_Nettle cells_, very small cells, chiefly in the tentacles, easily identified in permanent preparations as clear cells with small hairs projecting from them. See text-books for details of their structure.

_Spermary_, the region or organ where the sperm cells are formed.

_Ovary_, the region or organ where the egg cells are formed.

_Coelenterates_ (hollow bowels), sac-shaped animals, the digestive tract having only one opening; the body wall is of two layers.

_Directions._

Take a small aquarium to your table, set it down carefully and leave it undisturbed. Identify a hydra and watch it for some time.

_Observations on the living animals._

1. Describe the size and shape of a hydra when expanded. Disturb it slightly by shaking the aquarium a little, and describe its shape when contracted. Notice also the flexibility of the body. What do you infer concerning the hydra's possession of a skeleton? What advantage can it be to have a body so flexible?

2. How many tentacles has the hydra that you are studying? What does the hydra do with these tentacles when it is expanded? What is the probable object of such actions?

3. How does a hydra respond to contact? What seems to be the object of such a response?

4. Notice the location of the hydras in the large, undisturbed aquaria. Where are they placed as regards the light side of the aquarium? Of what value is such a response to light in their case?

5. How can a hydra locate the small animals which are its food?

How can it capture them?

6. What motions may a hydra perform, while remaining attached by its base? What are the results of these movements?

7. If you have happened to see a hydra move from one place to another, describe the process. If not, give the facts which lead you to believe that it is able to do so. Suggest all the methods you think it may be able to use. What is your opinion of the hydra's power of locomotion? Of what use is it in getting food; in escaping enemies; in following the fluctuations of the water supply? If you had to class the hydra as either one, would you call it a stationary or a locomotory animal?

8. Study budding hydras. Compare the bud with the parent hydra as to size, form and number and size of tentacles. Notice whether the bud moves independently or only with the parent. When does it separate from the parent?

9. In hydras collected late in the fall you may see another method of reproduction. If such material is at hand, notice small swellings near the proximal end and others near the tentacles. Eggs are produced in the lower one, the ovary, and sperm cells in the upper one, the spermary. Refer to your text-book for further details.

_Details of structure._

1. Using an entire mounted specimen and a section of hydra, identify the body wall and the central cavity. What is the extent of the central cavity? (Examine both the body and the tentacles.) Where does it open to the outside? What do you think is its use?

2. In the body wall, identify the endodermal and ectodermal layers of cells, separated by the mesoglea, which is usually stained more deeply. Study these cell layers carefully. What work ought each to do? What can you discover in its structure which would fit each layer to do its work?

3. In the tentacles, identify the nettle cells. Where are they? How are they arranged? About how many of them would be discharged if a small animal were to bump into a tentacle?

Summary of Important Points in the Study of Hydra

1. Name the different kinds of cells in a hydra. Which kind differs most from such a cell as the starfish egg? What work does this specialized cell do?

2. How much of a hydra's body may be set in action by touching a tentacle? Contrast this with the sponge. What do you infer concerning the nervous power of these two animals?

3. Look back over your notes and list the different kinds of work a hydra can do.

4. Can it do any more kinds of work than a paramecium or a sponge can? If so, give further details.

5. Can it do any of its work in any better way? Would you expect it to be able to? Why, or why not?

_Suggested drawings._

a. Hydra undisturbed, and hydra after being touched or shaken.

b. A hydra in successive poses to show its flexibility.

c. A hydra taking food.

d. Hydras to show reproduction in one or both ways.

e. A section of hydra, showing details.

Comparative Study of Coelenterates

_Materials._

Various coelenterates, such as hydroids, hydro-medusæ, jellyfishes, sea anemones, corals, sea fans, etc. Since nearly all the coelenterates except hydras are marine forms, these will usually have to be dead specimens, preserved in formalin or alcohol, or put up as permanent preparations for the microscope.

_Definitions._

_Colony_, as used in this group, a number of individuals descended by budding from an original one, and remaining connected.

_Polyp_, an individual coelenterate; one of the individuals in a colony.

_Observations._

1. How large is an individual specimen in the form you are studying? If the form is colonial, how large is the colony or portion of a colony you are studying? Estimate the number of individuals in it. Is the colony free-swimming or attached? If attached, to what is it usually fastened?

2. Compare the individual you are studying with a hydra, as to size and shape of the body, the location of the mouth, and the size, number, and arrangement of the tentacles.

3. Is there a skeleton? If so, describe it. What appears to be its use? In corals, notice the radiating partitions.

4. Has the specimen any nettle cells? If so, where are they located?

5. Are all the polyps of the colony alike? If not, how many kinds are there? How do they differ?

What is each kind best fitted to do? What is the probable result of this differentiation?

6. What kinds of reproduction, if any, does the specimen you are studying show?

Find out from books what other forms of reproduction are sometimes used by this animal.

_Suggested drawings._

a. At least one drawing of each coelenterate you study.

Summary of the Comparative Study of Coelenterates

1. How may polyps in colonial forms differ from polyps which live singly?

2. What variations in methods of reproduction are shown in this group?

3. Which of the polyps you have studied shows the greatest differentiation? In what ways?

4. What characteristic do you find common to all the coelenterates you have studied?

Review and Library Exercise on Coelenterates

1. What are the characteristics which distinguish coelenterates?

2. Give the classes of coelenterates, with the characteristics and an example of each.

3. What enables a hydra to stick to a support by its foot?

4. What are the processes in a hydra by which food is captured, swallowed, and digested?

5. What is the chief fact of interest about Hydra viridis?

6. Why do hydras reproduce all summer by budding and in the late fall by eggs?

7. What change would have developed a hydra and its offspring into a plant-like colony instead of into a group of individuals?

8. Why are ctenophores more easily seen in the night than other coelenterates are?

9. What relations may exist between hydroids and hydro-medusæ?

10. What are the advantages of a sedentary life? Of a locomotory one?

11. What is meant by the expression "alternation of generations"? Which animals are likely to develop alternation of generations, sedentary ones or locomotory ones? Why?

12. Give at least two differences between hydro-medusæ and true jellyfishes.

13. In the association between a hydractinia colony and a hermit crab, what advantages are derived by the hydractinia? by the crab? Define symbiosis. Give another illustration of it.

14. How are new coral colonies started? How are large colonies formed?

15. What are the conditions of life under which corals can grow vigorously?

16. Where are corals most abundant?

_Note._--Show by coloring the regions on a blank map of the world.

17. How may corals form a reef? Why do they, as a rule, form a reef instead of adding directly to the mainland?

18. Give Darwin's theory regarding the way a coral atoll may have been formed.

19. Where are fossil corals found in abundance? What does their presence prove?

20. What is polymorphism? Give an illustration. What may be a disadvantage of polymorphism? What may be an advantage?

21. In what ways is this group of economic importance?

4. A STUDY OF WORMS

_To show cells associated even more closely than in coelenterates, forming tissues and systems of organs._

#A STUDY OF EARTHWORMS#

The Living Earthworm

_Materials._

Living earthworms, some of which are left undisturbed from day to day, in damp earth with leaves of various plants scattered upon it.

_Definitions._

_Anterior end_, the head end, usually the leading end.

_Posterior end_, the end opposite the anterior end.

_Ventral surface_, the lower surface, usually the one which contains the mouth.

_Dorsal surface_, the one opposite the ventral surface.

_Somites_, the rings or segments of which some animal bodies are composed.

_Bilateral symmetry_, the symmetry usually shown by animals which have differentiated dorsal and ventral surfaces, and right and left sides. Animals which do not have such differentiated surfaces are usually _radially symmetrical_, but sometimes asymmetrical (without symmetry).

_Girdle_, the somewhat transparent band frequently found near the anterior end of an earthworm.

_Anal opening_, the posterior opening of the food canal.

_Setæ_ (singular form, _seta_), small bristles or stiff hairs. In the earthworm these are set in the body wall at definite intervals, and aid in locomotion.

_Cuticle_, in the earthworm a delicate, shining cover over the body.

_Egg capsules_, small, light-colored, spindle-shaped sacks, about the size and somewhat the shape of a grain of wheat, containing the eggs or young of earthworms.

_Directions._

Take a living earthworm to your table and keep it damp by placing it in a wet tray or upon moist paper. Identify the anterior and posterior ends, the dorsal and ventral surfaces, and the right and left sides. Identify also the somites and the girdle, the mouth with its projecting lip, and the anal opening.

_Observations._

1. Watch a living worm for some time. Does it seem to have a definite object in its moving? If so, what is it? Upon what sense or senses does it seem to depend for guidance? Which end usually leads? Why?

2. Over what sort of surface does it move most easily? Why? Watch it closely for some time and discover how it is able to move from place to place. (_Suggestion._ What is the function of the setæ in this process? How can you explain the alternate contraction and expansion of parts?)

3. From time to time, for perhaps a week, examine the leaves which were scattered where the worms could reach them. Have the worms moved them about at all? If so, where are the leaves left? Have any been eaten, in part or entirely? If so, is there any evidence of selection, either as to the kind of leaf or the portion of leaf eaten? If earthworms select food, what senses would be useful for the purpose? Have you any evidence that earthworms possess such senses?

4. Looking through the dorsal wall, notice the meandering red line, seen more easily in some regions than in others. This is the dorsal blood vessel. How long is it? Where is it wider? Where narrower? Notice its pulsations. How many times per minute does it pulsate? In which direction is the blood forced? Is there a corresponding ventral blood vessel? Place a small worm between two pieces of glass, so that you may see through it more easily, and identify the blood vessels encircling the digestive canal, near the anterior end. These are the so-called "hearts" of the earthworm. If possible, decide in which direction the blood flows through them.

5. The food canal, or alimentary canal, lies underneath the dorsal blood vessel, and is usually easily seen, especially if it is full of food. Notice it when the worm is fully stretched and again when it is contracted. How long is the canal? Why does it wrinkle when the worm contracts? Where does it open to the outside? Why does it need to?

6. Where do you infer respiration must take place in this animal? Why do you think so? What fits this surface for such a purpose? Why does an earthworm seem so uncomfortable when it is too dry?

7. Where do earthworms live? What conditions are necessary in their habitat?

8. When do earthworms usually leave their burrows? Why at that particular time rather than at another? Why does "the early bird catch the worm"?

9. What enemies do earthworms have? How are they protected against these enemies?

10. If you have found egg capsules when collecting worms, describe them.

External Morphology of Earthworms

_Materials._

Preserved earthworms, the larger the better.

_Observations._

1. In what respects are the dorsal and ventral surfaces alike? In what respects different? Why?

2. Why are the right and left sides alike?

3. In what respects are the two ends alike? In what different? Why?

4. How many somites are there from the anterior end to the girdle? How many under the girdle? How many from the girdle to the posterior end?

5. Where are the setæ located in a somite? How are they distributed over the body?

_Suggested drawings._

a. An earthworm, dorsal aspect.

b. An earthworm, ventral aspect.