THE JASMINE KINGDOM
I’d seen snails around my backyard on occasion. They appeared after rains, each about the size of a knuckle, waving their horns enthusiastically. I saw them most frequently in and around a thicket of jasmine growing at my back door. When I searched the deck beneath the jasmine, I saw that it was spotted with piles of scat. Josephine and I crouched down beneath the jasmine and looked closer. There were dozens of little turds, some draped in piles that seemed too large to have come from a snail.
“Ew,” Josephine said.
Something shiny white was wedged between the planks. I tugged it free and found I was holding a shard of what must have been a massive snail shell. The interior was pearly, and curved into a perfect spiral. From this low vantage point, I could peer into the jungle of vines. There must be a whole society of snails in there, pruning my jasmine from the inside out. “Society” isn’t too strong a word: Snails do communicate among themselves, and they coordinate their efforts. The USDA warned in a snail-farming newsletter that a team of gastropods imprisoned in a box can combine their muscular efforts to lift a heavy lid and escape. Crouching there, I marveled to have discovered a complex hidden world that had previously escaped my detection, though I walk by that very location several times every day.
A few hours of research taught me that the prodigious offerings on my porch were indeed snail poop. In my reading, I also came across a diagram of snail anatomy and was confused by the fact that the organ labeled “anus” seemed to be inside the shell. A little more digging confirmed that I was not misreading it: Snails poop on their own heads. Josephine laughed and laughed at this, but it doesn’t seem to bother the snails. The droppings slide out and onto the ground. If snails destroy your garden, you can accurately call them shitheads.
This inconvenient arrangement of anatomy is an accident of evolution, living evidence of unintelligent design. A snail starts out upon hatching with its gut in a straight line: The mouth is at the front, the anus is at the rear. But as the shell grows into a spiral, the body twists along with it. A bit of food eaten by a snail travels upward through the gut toward the apex of the spiral, then back down again.
ARCHITECTURAL GEOMETRY
If you shrank to a centimeter and walked up into an unoccupied snail shell, you would find yourself in a smooth white tube turning upward like a spiral staircase. If, like most snails’ shells, yours was dextral, you could run your left hand along the interior wall, the axis of the spiral. Turn around to face the opening, and you would see the passageway turning always to the right (dexter in Latin) as it opened. Some snails, however, are sinistral, with their spirals to the left, coiling clockwise. The orientation of a snail’s architecture influences its sexuality. The sexual organs of two snails will properly align only when they have matching shells.
As you continued walking up into your shell, you would find the walls rapidly closing in on you until you were forced to stoop, then crawl. If you were not claustrophobic, you could lie down and reach your arm up around the next curve. On the way back, you would notice the diameter of the passageway increasing dramatically until it became an echoing hallway. The sound of each footstep would ricochet off the curving walls, up to the spire and back down again, until there was a sea of echoes that sounded like waves on a beach. These echoes are a product of the mathematical properties of the shell. Each shell is a perfect logarithmic spire. Though they vary spectacularly in size and color, and though the spiral may be as squat as a cinnamon roll, as they are in my garden snails, or drawn out like a conch’s, every shell follows this geometric rule, its radius increasing exponentially as it opens outward. Mathematically, snail shells conform to the golden ratio, the value that biology employs hundreds of times in radial growth, and just the right pattern to grow spiral rings without creating a gap.
The shells grow, I learned, as snails exude minerals, which harden in place around the opening. Snails require an ample supply of calcium to build their homes, but calcium often is hard to find in forests and gardens. The snail, writes Bailey, “is the only known land animal able to find calcium by smell.” And because the snail carries chemical receptors in each of its tentacles, it can smell in stereo. By waving its horns, it can sniff out the direction of the mineral’s scent, and perhaps also gauge its distance. It also has retractable eyes at the tips of these “telescopic watch-towers,” to borrow nineteenth-century physician James Weir Jr.’s description. Snails’ eyesight is poor, able to detect light and movement but not much else. They taste with their lower tentacles. They have no sense of hearing. They experience the world mostly through touch and smell.
I ADOPT A SNAIL
I found a brown snail the size of a pencil eraser nestled beneath the curl of a pink camellia blossom. Inspired by Bailey, I picked the blossom and put it in a glass jar on my desk. I added half an eggshell for calcium and filled it with water. On that first night, the snail crept up from the flower onto the glass, affixed itself there, then retreated into its shell. In this position, I could examine it from every angle. My snail, like its relatives in the jasmine bush, was a brown garden snail, Cornu aspersum, the same species eaten in fancy restaurants. Cornu means horn-shaped, and aspersum means spattered, or strewn. Its shell was flecked with a dozen shades of brown, streaked with darker brown stripes parallel to its spiral. There was a new edge of shell, white and translucent, like a baby’s fingernail, about a centimeter wide. I could see the shell from both inside and out, because the snail’s foot was withdrawn deeply into the cavity, with a thin layer of slime around the edge of the shell gluing it to the glass. It stayed in this position day after day. The new shell growth darkened. The pattern of concentric lines emerged in the white like an image on a slow-motion Polaroid, but the snail was otherwise motionless and unchanged.
In the face of inclement weather, irksome dryness, or disagreeable banquet choices, snails withdraw into their shells and become dormant. “At the first hint of frost our snail feels the approach of a resistless lassitude,” wrote Ernest Ingersoll in his 1879 essay, titled “In a Snailery.” “Creeping under some moldering log or half-buried bowlder [sic], it attaches itself, aperture upward, by exuding a little glue.” They seal up the shell’s opening with a layer of mucus, which dries into taut parchment. If it is cold enough, the snail will retreat farther inward and stretch another barrier across the shell, creating an insulating layer of air. It will then spend the winter, in Ingersoll’s words, “snugly coiled in the deepest recesses of his domicile.” By putting their already slow life on pause in this manner, garden snails can survive temperatures down to 23°F. Scotland’s snails routinely hibernate for seven months of the year. And in some cases, dormancy can last several years. Snails of other species have revived after an interlude encased in a block of ice. If I didn’t tune my snail’s living conditions to its preferences, its patience would certainly outlast mine.
Sleeping Travelers
Snails nearly drove Charles Darwin mad. In a letter to a friend, the botanist Joseph Hooker, Darwin wrote, “I have for [the] last 15 months been tormented & haunted by land mollusca.” Darwin’s problem was that snails had been found on every island that naturalists had searched, and he could not conceive of a means by which snails could have leaped over the ocean to reach them all. This seemed a victory for the creationist idea that God had distributed the animals. If he could not explain how snails had reached the islands, it was a sign that some element of Darwin’s reasoning was wrong.
The solution lay in a snail’s ability to go dormant. Dormancy could, paradoxically, allow snails to move across great distances. After much frustration and anxiety, Darwin tried dropping dormant snails into seawater for varying periods of time. When one of these snails revived, Darwin wrote, it “quite astonished & delighted me. I feel as if a thousand pound weight was taken off my back.” A snail hibernating in the crevice of a branch could easily float six hundred miles in an ocean current, he calculated.
Darwin later realized that snails could al
so leap the oceans by sticking themselves to migrating birds. Scientists have confirmed that snails do hitch rides in this way, attaching themselves to bird feathers, mammal hairs, and insect exoskeletons: “a tiny snail has been known to catch a ride on the leg of a bee,” Bailey wrote.
Many species of snails are minuscule. One day, while watering the maidenhair fern on my desk, I noticed a little shell. It was empty, and barely big enough to cover the “o” on the back of a penny. I’d nearly passed it over as a speck of dirt, but some part of my brain registered its order and symmetry. It was only when I transferred it to a white sheet of paper (carefully—it was too small to pick up with a thumb and forefinger) that it revealed itself to me.
It must have lived in the fern. Perhaps there were others. What did it eat? And how had it met its end? Was it the victim of some tiny predator? I started imagining the food web that must exist in the pot at my elbow. What else have I been missing, I wondered, because I’ve never before taken the time to examine the dust?
Mollusk Moonwalk
After spending two weeks cemented to the glass, my snail moved to the bottom of the jar. I picked it up, thinking that it must have fallen because it had finally dried up. It was as light as a frozen pea in my fingers. I rolled it over. The shell opening had changed shape, and now looked more triangular than oval. Then I saw why: A foot was slowly emerging from the shell. Still worried that the snail might be desiccated, I quickly dipped it in water. Immediately the head emerged and the horns peeped out. I positioned it next to the camellia blossom. It steamed off my thumb and onto the petals while I waited (and waited).
There’s something transfixing about snail locomotion. They move without any visible sign of movement, like a wakeless ship ghosting over the water. It was miraculous to watch, as if I’d suddenly gained the ability to see plants grow or leaves change color.
A snail moves by flexing its foot, sending a series of tiny waves through the surface. These ripples briefly turn the mucus it secretes from a solid to a liquid, allowing it to glide. Snails are like cross-country skiers, but instead of pushing off with one ski as they glide on the other, they do it all on one ski, pushing with part of the surface and gliding on the rest.
A snail will sometimes “gallop,” lifting the forward part of its foot and jumping over a bit of ground. A galloping snail leaves a dotted track rather than a continuous trail of slime. There is one species that, when provoked, does a sort of wheelie, rearing up on the back of its foot and speeding off, relatively speaking.
The slime that snails use to walk is called pedal mucus. It is this that allows them to travel up walls and sleep upside down on the underside of leaves. “So tenacious is this exudation that some species can hang in mid-air by spinning out a mucous thread,” wrote Ingersoll.
As my snail traversed the petals of the camellia blossom, it waved its antennae expressively. At times they would stretch forward, at others they hung limp. It was easy to infer human feeling in these movements: yearning, excitement, curiosity, disappointment. Josephine, who had crawled up into my lap when she found me watching the reanimated snail, smiled at these antics. The snail’s young body was transparent and we could plainly see the dark nerve pathways running from its eyestalk to form tiny dots in the bulbous tips. When Josephine swept a hand out to touch the tentacle, the snail sensed the oncoming mass and recoiled. Because we could see through the skin, we were able to watch the eyes and their dark connecting cables retracting through the antennae and back into the head. If the antennae are telescopic towers, the eye is the watchman that climbs the tower and can just as quickly retreat.
The snail seemed uninterested in the water and the eggshell that I had set in its path. Surmising that the camellia did not suit its tastes, I offered it a crisp leaf of butter lettuce. The snail’s antennae strained toward my offering and it sailed forward with what seemed to be great interest. Through my hand lens I could see its open mouth and an upper row of teeth chomping down on the leaf. It had a cartoonish overbite—the snail was completely lacking in the chin department—that I found endearing. As I peered at it I could hear, faintly but unmistakably, the sound of its thousands of tiny teeth crunching lettuce.
Snails are hermaphrodites. They can fertilize their own eggs, and when they mate they both give and receive sperm. To ensure that its partner will use its sperm, a snail can lance its mate with a hollow “love dart.” These barbed harpoons contain an injection of sex hormones, which increases the chance that the harpooner will become a father. The darts are made of calcium carbonate and kept in a special interior sac. Garden snails carry just one dart at a time. They are typically about an inch long and gently curved, with four blades running along the length like a hunting arrowhead.
SLOWING DOWN
My snail fled its jar the night after it revived. I wish it well. I hope it found its way outside, or into the moist soil at the base of a houseplant. Bailey, after eventually growing well, released her snail, along with its progeny.
Most people, I think, are not so fond of snails. As Ingersoll wrote, “Two-thirds of the persons to whom I show the little land and fresh-water mollusks in my snailery either start back with an ‘Oh! the horrid things!’ which causes me some amusement, or else gaze straight out of the window, saying languidly, ‘How interesting!’ which hurts my pride.”
I can understand. Most people notice snails only when they come to eat their gardens. They are so fundamentally alien from us that they provoke a natural fear of the unknown. But if you have a little patience, this strangeness makes snails wonderful for watching. Reflecting on her relationship with her snail, Bailey told her doctor, “Watching another creature go about its life . . . somehow gave me, the watcher, purpose too. If life mattered to the snail and the snail mattered to me, it meant something in my life mattered, so I kept on.”
Meaning is hard to come by if you are a solitary entity. If you have doubts about your own usefulness and purpose, it is all but impossible to answer those doubts while unmoored. When you are able to affix yourself somehow, to bridge the abyss with a relationship with another creature of any sort, it’s easier to make the case that there is some way in which the whole of creation matters, that it has, if not a purpose, at least an invigorating vitality. I find satisfaction in hitching myself to the universe as an observer of this energy, manifest in wonderful complexity. I matter, because it matters. Human self-awareness allows us to question our purpose. But that self-awareness also allows us to watch ourselves experiencing wonder, curiosity, and the delight of discovery, and therefore to value those things. Our role may be fulfilled, perhaps, simply by paying close attention. Maybe that’s the meaning.
CONCLUSION
The species that I’ve written about here are, at best, invisible, and at worst, reviled. We honor least the nature that is closest to us. As Courtney Humphries put it in Superdove, “We create and destroy habitat, we shape genomes, we aid the worldwide movement of other species. And yet we seem disappointed and horrified when those plants and animals respond by adapting to our changes and thriving in them.”
Because they are associated with human disruption, the organisms that spring up from our footprints look like corruptions of nature. But I’ve come to see it the other way around: These species represent nature at its most vital and creative.
Nature never misses an opportunity to exploit a catastrophe. When humans bulldoze and pave, nature sends in a vanguard of species that can tough it out in the new environment. These invasive species are not nature’s destroyers, but rather its creators. They begin setting up food webs, they evolve and diverge into new species. Because humans purposefully import exotic plants—along with the insects, seeds, and microbes we accidentally bring in from around the world—cities are remarkable centers of biodiversity. These creatures crossbreed, hybridize, eat one another, form cooperative relationships, and evolve. And so, at a time when thousands of species are at risk of extinction because of our destruction of wilderness, new species are springing
up in the new habitats we have created. And it’s not just one or two new species: The conservation biologist Chris Thomas, who studies the emergence of species in human-dominated areas, has estimated the increase in plant species over the last 150 years is just about equal to the extinction rate for mammals.
We tend to think of nature and civilization as being irreconcilably opposed: Civilization’s gain is nature’s loss. But in fact, cities have become prime habitat for speciation, hybridization, and, in short, rebirth. Certainly, civilization has upended the status quo in nature, but it is also proving to be a vehicle for a natural renaissance.
This doesn’t mean that we should stop worrying about extinctions and the environment. Earth as a whole is going to be fine, but the Sumatran tiger is not going to be fine. And many humans are not going to be fine. By altering the climate, we are making the world less hospitable to humanity too, and the poorest among us have already begun to suffer.
Unseen City Page 18