Inquiry into the Zen of
Museum of Natural History & Science
Cincinnati Museum Center
Director of Education
1995 ASTC Annual Conference
San Diego, California
October 15, 1995
"They are not brethren,
they are not underlings; they are other nations, caught like ourselves in the
net of life and time, fellow prisoners of the splendor and travail of the Earth.
-- Henry Beston
make good tools for inquiry --- they are familiar yet still alien enough to
invoke interest. Many people have dissected a worm in biology class but that
is a far cry from getting to know a living worm up close and personally. As
children, as well as adults, get caught up in our increasingly high-tech world,
the reality of the world around us threatens to become lost. I think the point
of this avenue of inquiry is to get people to appreciate the lives of other
living things with which we share this Earth.
Worm Facts (or
things to remember when you are about to impale a worm on your fish hook):
Earthworms in general
- have been around 120
million years. They evolved during the time of the dinosaurs; hominids have
been around only about 4 million years and Homo Sapiens about 25O,OOO years.
- enrich and aerate the
soil. Darwin found that worms turn over the top 6 inches of topsoil every
- can grow to 11-feet-long
-- this species lives in Australia.
- lack a brain but have
nerve centers (called ganglia).
- lack eyes but can sense
light with photoreceptors.
- are hermaphrodites (both
sexes in one animal) but cross fertilize.
What You Need: Worms
--- nightcrawlers (Lumbricus terrestris) are large and easy to observe. Any bait
shop will carry them though they may be seasonal so check it out. Or, of course,
you can dig them up in your yard if you happen to be in the cooler areas of this
country which they have invaded. Invaded! ! ! Yes, they are aliens introduced
from Europe probably in the earth surrounding the roots of imported plants. Native
worms tend to be smaller but smaller worms are easier to shine light through to
see what the "innards" are doing as the animal moves. Worms can be kept alive
for long periods. A dozen large L. terrestris are surviving with no apparent ill
effects in a large whipped margarine container filled with good potting soil mixed
with corn mean, oatmeal and coffee grounds (smells great!). Just keep the soil
moist and replenish the food supply once a week.
- are an exotic, alien
species introduced from Europe in the soil around plant roots
- live 5-10 years
- can grow to a foot in
- burrow to six feet or
- have 5 "hearts"
- have red blood (with
hemoglobin like us)
Procedure: The role
of the facilitator is to move the program along without giving direct formulae
as to what to do to the participants. That's not easy to do. The purpose of the
activity is for people to ask questions, predict what might happen, then test
it out. I usually give a brief introduction and a few comments about worms especially
reminding them that worms are living creatures and are to be respected and not
harmed by any of the activities They are not weapons of terrorist aggression to
be dangled in front of someone's f face or put down someone's shirt. They need
to be kept moist. They breathe through the surface of the skin and this surface
needs to be moist just like the areas of our lungs where gas exchange takes place.
Glands in the "different" looking band near the anterior (front) end as well as
all over the body secrete mucous to keep the body moist. Thus the worm should
be placed on a wet paper towel. Being in a tray is helpful but not mandatory.
- a tray is nice but not
- paper towels
- a spray bottle so that
people can keep the worms moist.
- different chemicals
(alcohol, vanilla extract, liquid smoke, etc.)
- dry sand
- a clear plastic tray
so that you can shine a light from beneath the worm
- a flashlight
- magnifying glasses
- ice cubes
It helps for people to
work in pairs. This way they can generate more questions and suggestions for
testing hypotheses. To get things going, ask each one to introduce themselves
to their worm partner. Ask them to think about where they look when they introduce
themselves to other humans. They look at the face. Does a worm have a face?
Indeed, does a worm have a head? They can begin their investigation into worm
ways there. Your role is to circulate and move their inquiry along. When they
ask questions try to get them to suggest ways that they could test to learn
the answer. If they don't come up with questions, help them along by asking
a question and having them testing for answers. Also keep in mind that different
worms, like people, respond differently in the same situation. So, if two teams
try the same experiment and get differing responses ask them what they would
have to do to really verify their results. Lead them to the conclusion that
repeatability is essential to making any firm conclusion and many trials need
to be run before you can say anything is true with any certainty. Some questions
that could come up are:
Wrap-Up: Have each team
tell the group as a whole at least one thing they learned about worms as a result
of this activity. This usually brings up things to discuss and you can offer more
insight into wormness as topics arise.
- Is there a top side
and a bottom side? Tell them to think of a way to find out. Hopefully
they will turn the worm over to see if it looks physically different (it does).
Have them run a finger along the underside. They should feel the setae (stiff
hairs) which the worm uses to anchor in the soil and help propel it along.
Have them observe how the worm will right itself if overturned.
- Does the worm have
a skeleton? Ask them what they think based on picking the worm up and
gently feeling it. Go over how a skeleton helps us move by being an attachment
site for our muscles. Ask them if they think a worm has muscles.
- If it doesn't have
a skeleton how does it move? Have them observe how a worm moves and come
up with a scheme of how the muscles work based on their observations. Worms
have a hydrostatic skeleton, i.e. it is a bag of water. Contraction of circular
muscles will extend the worm Contraction of longitudinal muscles will make
the body contract.
- Does a worm prefer
wet to dry areas? The fact that you start out with the worm on a wet
towel seems to indicate this preference but ask the participants to test for
their worm's preference. Just observing the worm as it comes to the edge of
the wet paper towel should lead to some conclusion. Or a dry paper towel can
be folded in half and placed on top of one half of the wet towel to see what
- Does a worm eat?
Lumbricus is a fairly thick worm but if you they can make it stretch
out on a clear piece of plastic and shine a light up through the body, the
digestive tube can be seen. A worm is essentially a tube within a tube. The
mouth is a toothless opening on the underside of the "head's" first segment.
The digestive system is a linear tube with an enlarged portion which can grind
up leaves or other organic debris on which the worm feeds. The feces are called
castings and serve to enrich the soil.
- Does a worm have
babies? This is just informational. Unless it is spring you probably
won't be able to observe mating. Worms are hamaphrodites, they are both male
and female at one time. Why would this be a good situation? Because any worm
encountering another worm will immediately know that it can mate with the
other worm. They don't have to spend much time determining whether the other
worm is of the same or different sex. Worms mate in the spring. The genital
openings are anterior to the clitellum, that band near the front end that
is enlarged and of a slightly different color. The worms exchange sperm simultaneously,
separate, then a few days later the clitellum secretes a tough cocoon filled
with albumin (like egg white) which picks up the eggs and sperm as it passes
forward. The cocoon seals when it passes off the worm's head and fertilization
takes place within the cocoon. Development takes place within the cocoon and
the young hatch in 12-13 days.
- Do worms have soil
type preferences? Have the participants come up with ways to test for
this. For example put a ring of dry sand around the worm to see how it will
react. When it appears not to like to cross over the sand ring ask why. Is
it because it is "scratchy" and uncomfortable and sticks to the worm's skin?
Can a worm find a break in the sand ring repeatedly? What does this tell you
about the "cognitive" abilities of worms. How can you test to see if it is
the discomfort of the sand the worm objects to or if it is the dryness? (Participants
can wet the sand). Explore other types of soils.
- Worms live in the
dark .Do they have eyes? How do they react to light? Worms don't have
eyes like you or I have. But they do have photoreceptors that detect light.
These are mostly concentrated in the anterior end. Have participants test
to see if worms can detect light from dark. (Put a sheet of paper over one
end of the tray and see if the worm can find it.). Or, often the worm will
crawl under the wet paper towel, which in itself indicates it is seeking a
darker space. Try sprinkling dark dirt in a winding path on top of the wet
towel and see what happens. The worm will follow the trail of darkness stopping
where the trail stops.
- What does a worm
do in the winter? I.e., does a worm respond to cold? This is what the
ice cubes are for, but have them available and let participants come up with
a test. It can be as simple as putting a cube down on the papa towel and seeing
if the worm will avoid the cube and cold melt water. After making predictions,
and observing the worm's reactions have the participants suggest what a worm
does in winter. Below the frost line the earth tends to stay at a constant
temperature most of the winter. Worms just burrow deeper in winter.
Barnes, Robert D. 1980. Invertebrate
Zoology. Sauders College. Philadelphia, PA.
Holley, Dennis. 1994. Animals
Alive! An Ecological Guide to Animal Activities. Roberts Rinehart, NY.
Kneidel, Sally Stenhouse.
1993. Creepy Crawlies and the Scientific Method. Fulcrum Publ., Golden, CO.
Stevens, William K. 1995.
It's Natives vs. Newcomers Down in the Worm World. New York Times, March 28.
Reprinted with permission
of the author.
© 1996 Exploratorium,
3601 Lyon St., San Francisco, CA 94123