Territorial Imperative in Planaria

A high school honors student takes responsibility for a series of deliberate deaths

A planarian lacks an anus, but it can regenerate a whole individual from a part, so these flatworms are normally used for regeneration experiments and not the kind of behavioral study I had planned for my eleventh-grade science project. Planaria appear cross-eyed, but they possess only eye spots, ocelli, which sense the intensity of light. I was interested in the relationship between light and their behavior, so I set ten worms in each of three Petri dishes in a small bookcase in my closet, where it was dark. In the middle of the night, I sat in there and changed a naked bulb—white, red, yellow—while making notes about their behavior. In the dark, momentarily flashlit, they moved little. Under red, they turned cannibal, eating their fellows in the dish.

My science teacher—let’s call him T.O.W.—asked me why I wore a huge white shirt to class. Oversized shirts were the girl fashion statement at the time, and I wore my dad’s size XXX. When my arms slipped out of the giant armholes, the shirt draped me like a poncho.

“Your parents let you go to school like that?” he asked.

“They don’t really let me or not let me,” I answered. My hands fluttered in the sleeves before they took flight in air and landed on the lab desk next to the faucet, a tall goose-necked pipe. I put my thumb over the nozzle. Without thinking, I turned on the water, blasting T.O.W. with the spray and showering the gold frog tack squatting on his tie.


Squeezed by a collar bolted shut and noosed under a half-Windsor, his neck seemed to elongate at the same time that his black brush mustache twitched parallel to his raised eyebrows.

Since he said parents, I wondered whether he knew my mother was dead. I knew that was the kind of personal information teachers shared, prompted by counselors on the lookout for emotional decompensation. I hoped he wasn’t being nice to me because he felt sorry for me. My English teacher, the first day I came back to school, called me to the front to read Shelley’s poem “Mont Blanc.” I wondered if Mrs. Seibert used the poem as code to communicate her secret sympathy for me because my mother had been French. Or maybe she listened for a tremolo in my voice that warned I was falling apart. I knew how to appear normal to my teachers: I always did homework. Came to class on time. Listened and took notes. My emotional façade was bullet proof. My dad had been in the army. We were brought up to be brave. After Kennedy’s assassination, our mother gathered us around the television to watch the funeral. “Look at John-John,” she instructed. “He doesn’t cry. He is so brave.”

By the time T.O.W. was my teacher, my mom had been dead a year. 


Because planaria have no eyes, if one bumps into an obstacle while moving forward, it will automatically veer and continue onward. This ability to respond to environment, called “irritability,” is one of the seven life functions counted in the acronym GRIMNER: growth, reproduction, irritability, movement, nutrition, excretion, respiration. Irritability was my favorite of the life functions. 


T.O.W. had ordered the earthworms from a biological supply company and pulled them out of the formaldehyde jar one at a time with tongs. We were required to identify every part of the worm. Split longitudinally with the sides peeled back and pinned to the wax bottom of the tray, mine lay open like a book. Its neatly dissected body displayed my handiwork; the five aortic “arches,” or hearts, resembling knotted dental floss, had been teased away from other tissue. But something in the body cavity defied recognition—a rubbery string. Intending to scrutinize this unknown stringy thing, I meant only to raise it with tweezers. Like a rubber band, it stretched before it broke and came popping out of the worm, sticking to my hand. Shaking my hand only made it stick more. Pretending a casualness I never felt, I sauntered over to the windows, open above a courtyard with azaleas and Spanish bayonets, and took a breath of fresh air. When I tried to fling the organ into the leaves, it jumped to a different finger, so I brushed it onto the sill. T.O.W. suspected something funny, so he said, “Go back to your station.”

When he came around to my worm, he quizzed me on the body cavity. I was mentally congratulating myself for naming each part he indicated when he surprised me.

“Something strange. Your worm has no sex organs.”

“Oh. That’s what that was.”

His mustache slanted as his upper lip tensed in what I came to know was his quizzical look. Having transferred from Catholic school, I knew to tell the truth.

“I threw it out the window. I didn’t know what it was.”

T.O.W. reached down to run his finger along the worm. “Feel it.”

I did. “The setae of your worm are on the dorsal side.”

Setae are stiff, short hairs like bristles. “You dissected it upside down,” he added.

Accomplishment or criticism? I couldn’t tell.

Still, I became his star student, the one he took to the night class he taught at Jacksonville University in a large, narrow lecture hall. My seat at the back seemed high enough to touch the ceiling. Narrow steps slanted steeply below like an Aztec pyramid. T.O.W.’s class was studying respiration. When he asked for the formula for the Krebs cycle, no one replied. A clot of college students sat motionless in severe blue light, with T.O.W. standing behind the desk, its surface a black slab like a sacrificial altar, the chalkboard blank behind him. Dramatic silence ensued. Then: “Marilyn, do you want to try?” In Girl Scout spirit, straight-backed and earnest, with my hand mentally placed over my heart, I answered, “With one or two molecules of ATP?”

In Catholic school, chubby girls like me never had the privilege of crowning Mary the Queen of the May, an honor which entailed climbing the steps of the outdoor shrine with a coronet of roses in both hands, standing in blessed golden light beside the blue-veiled Mary looking up to heaven, and dropping the crown on her head. In front of the whole school. Usually, the regular-shaped girls with clear skin and curly caramel hair ascended the steps. In the auditorium of the college class, I felt as if I had won a race purely by running, not by racing.

When T.O.W. recounted the moment to my high school class, I glutted like a tick on his approval.


“I have three pairs of khaki pants,” my dad explained to anyone at the elementary school who showed the slightest interest. After he retired from the army, he taught sixth grade. Taking cues from his previous career in the military, he devised a civilian uniform. Multiple shirts went with the khaki pants. On a cold day, he added a windbreaker. The crepe soles of his comfortable shoes scrunched when he walked.

Which one of his three identical outfits was he wearing that day when he clutched me to him, asking, “What are we going to do?” The medic had disappeared back in the bedroom. The ambulance, parked in our driveway, looked like a missile pointed at the door. On the way out, the medic carried his bag as if it was loaded with bricks. Mom wore a housedress, the pattern a relentlessly repeated geometric like the tiles of a bathroom floor. She used to buy the material and patterns, and take them to a dressmaker. She was barefoot. Her dress was blue. Her face turned color; the pink flush faded.

The original color of a human being was gray—who knew?

My little sister, Chantal, always loved our mom the best. When our mother lay in bed at twilight, lights off, a late afternoon glow of yellow dusk bent through the Venetian blinds, a washcloth over her face from a migraine, Chantal brushed her hair so it spread across the pillow in gentle waves. I tested our mother more, serious as a gun safe even at seven, asking, “Would you eat a lizard to save my life?” “Would you eat a frog to save my life?” She said she would. She would even eat a worm. What mother wouldn’t?


We fought like red-lit planaria after her death. By age fifteen, Chantal stood close to six feet tall and outweighed me by twenty pounds. Her height gave her the advantage when she wanted to hurt me, like the time I rode her piggyback with my forearm around her throat. She backed into the wall, slamming me against it, leaving spiderweb cracks in the pink paint. We struggled in the room for a couple of turns. I knew I had to choke her till she wilted or she would kill me. Sometimes, it was two against one, with my brother taking her side, like the day I got home from school late. Mike or Chantal must have picked up the house key; the two of them locked all the doors. Looking for the easiest way to break in, I slipped around to the front of the house and pulled out the screen from the chest-high bathroom window. Blinds hung there so I couldn’t see in. I stretched to raise the glass higher before I hooked a heel on the sill, slid a leg through, pulled myself up and balanced there, easing the glass up farther while the screen’s track dented the back of my thigh. Then, someone inside pulled the window down, pinning my leg against the track. The house was chomping my leg. I screamed until invisible hands inside lifted the window.

The purple bruise, which started behind my knee and ran up beyond my hemline, attracted attention at school. I was called into a counselor’s office. She quizzed me about my family life. This was public school. Finally, she asked, “What happened to your leg? Did someone . . . hurt you?”

I could not wait to tell her.

Confession came naturally to me.

All three of us were confirmed at Christ the King Catholic School, but I was the only one who stayed through eighth grade. In fifth grade, Chantal shot a dirty look at the principal, Sister Ethelberga. When my sister scowled, her eyebrows stood on end like porcupine quills, and her eyes discharged lightning bolts; the nun said Chantal had given her the evil eye, and assigned her Saturday detention. Chantal broke her arm right before detention, so she showed up Saturday morning with a cast from wrist to elbow. That didn’t stop Sister Ethelberga, who made her scrape gum off the bathroom floors for three hours. With the good arm.

Transferring out, Mike also dodged the nuns, but the nuns loved me, even—especially—Sister Ethelberga, who called me, with an Irish accent, “Marrrrlin,” like the fish. Irresistibly chubby, I was poked and prodded like a brioche for my cuteness. My neckless head was crowned by a Prince Valiant haircut, as if a cereal bowl dictated the length of my locks.

Like Sister Ethelberga, all the religious at Christ the King stopped at nothing to prepare us for a virtuous life. A priest even showed up to poll our seventh-grade class about our future plans. Sister Martina had prepared us for this conversation; after I told her I wanted to be a priest so I could talk directly to God, she explained that only men could be priests. From Bible stories, I knew martyrs ran the fast track to heaven. And the best kind of martyr was the virgin martyr—which women could be.

So when the priest asked what I wanted to grow up to be, I voiced my new-formed ambition: “I want to be a virgin martyr.”

Although both men and women could be martyrs, usually the women were the virgin ones. Not to mention there was also something sexy about martyrdom, like the in-built magnetism of pink-skinned Saint Sebastian. Even if not marked with a ribbon, the page in my missal always fell open on his twisted torso, bound by rope and perforated by arrows. Blood oozed out from the arrow slits and dripped down his stomach. With his head tilted back and eyes focused on the ceiling or heaven, I just wanted to lick the page.

The priest halted in his tracks.

A classmate said, “You can’t grow up to be a virgin martyr.”

“Yes, I can.”

“No, you can’t. You can’t grow up if you are dead.”

So I changed: “Well, then, I want to be a doctor.”

Sighs of relief all around.

“No one said she wanted to be a saint,” the priest said. 


Three nuns made a procession the day they introduced the portable lab to our classroom. Excitement electrified the air as my seventh-grade class clustered up front to receive it. From down the hall came Sister Margaret Rita—with her stern eyebrows parallel to the white band over her forehead, her black dress snapping at her ankles—pushing the brute black cube on steel wheels. It resembled a war machine, like Leonardo da Vinci’s armor-plated tank. Sister Mary Joseph—in her early sixties, with fine red veins in her nose and gold-rimmed glasses, and her face so squeezed by her wimple that it resembled a pan of dinner buns—followed at Sister Margaret Rita’s elbow. Sister Ethelberga followed at the end of this procession, her stature and long gown giving the impression she was floating.

The lab sported a sink and goose-necked faucet and attachments for gas to run a Bunsen burner. We drew closer. Sister Margaret Rita moved with surprising grace as she fixed the gas hose to the burner and lit the flame. Two spots of red glowed on her cheeks. Only her face and hands showed bare flesh. The nuns may have dedicated their lives to God, their bodies encased in long black dresses, but now that I have had some experience of the world, I suspect the nun’s secret: passion inflamed her cheeks. The nuns were teachers, and every teacher I know loves material stuff. Language alone cannot carry the ideas and thoughts of education; objects drawn from the world are essential to show, rather than merely speak, the truth of ideas.

Even the federal government understands this passion of teachers, who get an automatic tax write-off for supplies they buy with their own money.

Sister Margaret Rita got her lab.

“See this,” she said, and we watched as the flame started up. She turned a knob or a key on the Bunsen burner, and the flame grew until it cast a shadow on her white bib. Little ribbons of black smoke drifted up the end of the flame, and if she wasn’t careful, the soot might smudge the ceiling. I would not have minded the accidental increase of gas to the flame, the halo of soot on the ceiling. That way, every time we sat in this classroom, I could look up and say, “This is where Sister Margaret Rita blasted the flame.” I could imagine her turned into flame, her body dissolving as she rose to heaven, the habit crumpled on the linoleum beneath her.

If I opened my missal to my favorite page, Saint Sebastian might eye the damage from the Bunsen burner.

Or watch the oily residue of Sister Margaret Rita. 


When my science project won a prize at school, it moved on to the regional competition, which was held at the Regency Square Mall. Even though my planaria experiment was classified as psychology (a soft science compared to biology or chemistry), I reveled in whatever glory could be found in talking with passing shoppers—who took one look at my title, “Territorial Imperative in Planaria,” written on my poster in lurid red caps, and then asked, “Is there a spewing volcano here? We want to see the volcano.” I had brought a couple of Petri dishes of worms, but the nearby anole lizard project—anoles have a pineal gland that functions as a third eye—drew even the magma-seeking shoppers. How could a tiny worm with no body cavity and only one orifice compete with a two-and-a-half-eyed vertebrate? My planaria, evolutionarily behind the curve, offered little to tired shoppers, and by the end of the day, the Petri dishes stood half empty because, no doubt, the little buggers had defended their territory by eating each other. Still, for all its limitations, I remained loyal to the flatworm, even if it used its own mouth for an anus.

It was like having an ugly boyfriend.


I stayed with T.O.W. as I progressed to Advanced Biology. For my senior-year science project, I decided I wanted to save the world from starvation. No vertebrate can digest cellulose directly; enzymes from bacteria are needed to do so. These bacteria live in different parts of the gut: for cows and other ruminants, this digestion takes place in the foregut, which is part of the stomach; animals with simple stomachs, like horses, rodents, and rabbits, send chewed food through to an organ called the cecum, in the rear gut, for further digestion. Humans have a cecum, too, though it’s vestigial. What if I could culture cellulose-digesting bacteria and thereby transform grasses and woody plants into a food source that humans could digest? The lawns of the world could sustain thousands of people.

First, I needed bacteria from an animal’s cecum. A girlfriend’s boyfriend brought me a dead squirrel he’d shot while hunting. I took the squirrel to school, and T.O.W. helped me dissect out the cecum. At the first cut, an odor oozed out. Not formaldehyde. A mix of rank and sour. “The body has its own smell inside,” T.O.W. said. The bacteria failed to grow. We needed a fresher animal.

So I bought a mouse. At the pet store. A white mouse with pink skin and stiff, twitchy whiskers and a pink tail. It seemed curious. It explored every corner of the box with a stunning display of irritability. T.O.W. was going to euthanize it for me. My twelfth-grade mentality pitched this to me in scientific terms: T.O.W. would convert the mouse into an object of dissection, like the pickled things he pulled out of jars for us in class.

When he said, “OK, it’s ready,” I went back to my lab station. Pinned the mouse in the tray. Opened it up. With scissors, I cut. I made big, irreparable cuts. The sides lay peeled back. There, I saw a little muscle the size of a bean. It was pulsing. The mouse lay cut open like a dress pattern ready for assembly. So open it could never be closed. I waited for the heart to stop. It kept beating. The lungs collapsed. The heart kept beating.

I gasped. “It’s alive.”

T.O.W. rushed in with the ether cloth and put it over its mouth. At least, I think that is what he did. I turned my back. I went to the window.

“It’s ready now, Marilyn,” he said.

Mixed feelings flooded me. Ashamed that I had fallen apart in front of my idol, my teacher, who had inspired me to memorize the text book, who had opened the biological world to me, peeling back its secrets one by one—the order and progress of the Krebs cycle, the attributes of life—I agonized that T.O.W. would consider me girly and weak, sentimental, all the adjectives commonly used to justify the limited number of women in science. Conscious of waiting black eyes, I took the inoculation needle, inserted it in the cecum, and collected bacteria. Made the zigzag mark on the Petri dish gelatin. Covered the dish. Labeled it. Put it on a shelf. But I did not care about the bacteria any more. I did not care that my technique would save the world. I always knew it would not.

I knew what I had done: extinguish life.

For nothing.

I could recite the Krebs cycle over the mouse’s shell, and I could parse its being by GRIMNER, but it would never regain life. Mitosis would not double its cells. It could never regenerate. Like any complex, multicellular organism, its life was defined by the heart at the center of its being. In taking one small life, my hand became implicated in all the others, the accidental deaths and the deliberate ones, as if a single thread webbed all creation. The tears that came later fell for every living thing. The dead president, the dead mother, the dead mouse wound themselves into one excruciating knot that made an indigestible ache in the center of my stomach. Since then, for me, death has always come sudden and untoward, never sublimated into something higher by either God or reason. I knew death as discrete acts, sequential but not transformed, strung along a wire like beads.

About the Author

Marilyn Moriarty

Marilyn Moriarty won the 2014 Faulkner Society’s Gold Medal for Best Essay. Her writing has been published in the Antioch Review, the Kenyon Review, Nimrod, Quarterly West, and others, and she is the author of Moses Unchained (winner of the AWP Prize for Creative Nonfiction) and a textbook, Writing Science through Critical Thinking.

View Essays