Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between 

the surface of the ocean and a depth of about 3,300 feet—as far as most light can reach. Most of them are extremely delicate and can be 

damaged by a simple touch. Sonke  Johnsen, a scientist in biology, says, “These animals live through their life alone. They never

touch anything unless they're eating it, or unless something is eating them.”

And they are as clear as glass. How does an animal become see-through? It's trickier than you might think.

      The objects around you are visible because they interact with light. Light typically travels in a straight line. But some materials slow and

 scatter(散射) light, bouncing it away from its original path. Others absorb light, stopping it dead in its tracks. Both scattering and absorption

 make an object look different from other objects around it, so you can see it easily.

But a transparent object doesn't absorb or scatter light, at least not very much, Light can pass through it without bending or stopping.

That means a transparent object doesn't look very different from the surrounding air or water. You don't see it —you see the things

behind it.

   To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they

contain pigments(色素) that absorb specific colors of light. But a transparent animal doesn't have pigments, so its tissues won't absorb

 light. According to  Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

Animals are built of many different materials—skin, fat, and more—and light moves through each at a different speed. Every time light

moves into a material with a new speed, it bends and scatters.Transparent animals use different tricks to fight scattering. Some animals are

simply very small or extremely flat. Without much tissue to scatter light, it is easier to be see--through. Others build a large, clear mass of

 non-living jelly-lie(果冻状的)material and spread themselves over it .

    Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light 

exactly as much as water does. They need to look uniform. But how they're doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process. When they die, they turn a non-transparent milky white.

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    In the famous fairy tale, Snow White eats the Queen's apple and falls victim to a curse（诅咒）;in Shakespeare's novel, Romeo drinks the poison and dies; some ancient Chinese emperors took pellets（药丸）that contained mercury（水银）, believing that it would make them immortal, but they died afterward.

    Poison has long been an important ingredient in literature and history, and it seems to always be associated with evil, danger and death. But how much do you really know about poison?

    An exhibition, The Power of Poison, opened last month at the American Museum of Natural History in New York, intended to give the audience a more vivid understanding of poison.

    The museum tour starts in a rainforest setting, where you can see live examples of some of the most poisonous animals: caterpillars（毛毛虫）, frogs and spiders. Golden poison frogs, for instance, aren't much bigger than a coin, but their skin is covered with a poison that can cut off the signaling power of your nerves, and a single frog has enough venom to kill 10 grown humans.

    "Poisons can be bad for some things," Michael Novacek, senior vice president of the museum, told NBC News. "Yet they can also be good for others."

    A poisonous chemical found in the yew tree is effective against cancer, which is what led to the invention of a cancer-fighting drug called Taxol.

    The benefits from natural poisons are not limited to just medicine. Believe it or not, many substances（物质）that we regularly ingest（摄入）-chili, coffee and chocolate-owe their special flavors or stimulating（提神的）effects to chemicals that plants make to poison insects.

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    Our “Mommy and Me” time began two years ago. My next-door neighbor and fellow mother, Christie, and I were out in our front yards, watching seven children of age 6 and under ride the bikes up and down. “I wish I could take one of my children out alone,” said Christie.

    Then we worked out a plan: When Christie takes one of her children out, I'll watch her other three. And when she watches two of mine. I'll take someone out.

    The children were extremely quick to accept the idea of “Mommy and Me” time. Christie's daughter, McKenzie, went first. When she returned, the other children showered her with tons of questions. McKenzie was smiling broadly. Christie looked refreshed and happy. “She's like a different child when there's no one else around,” Christie shared with me quickly. With her mother all to herself, McKenzie didn't have to make an effort to gain attention.

    Just as Christie had noticed changes in McKenzie, I also discovered something different in each of my children. For example, I am always surprised when my daughter, who is seldom close to me, holds my hand frequently. My stuttering (口吃的) son, Tom, doesn't stutter once during our activities since he doesn't have to struggle for a chance to speak. And another son, Sam, who's always a follower when around other children shines as a leader during our times together.

    The “Mommy and Me” time allows us to be simply alone and away with each child-talking, sharing, and laughing, which has been the biggest gain. Every child deserves to be an only child at least once in a while.

    It took place at the Biltmore Hotel. My grandmother, my mother, and I were having lunch after a morning spent shopping. I gladly ordered a Salisbury steak. When brought to the table, it was accompanied by a plate of peas. I do not like peas now. I did not like peas then. I have always hated peas.

    “Eat your peas,” my grandmother said.

    “Mother,” said my mother in her warning voice. “He doesn't like peas. Leave him alone.”

    My grandmother did not reply, but leaned in my direction, looked me in the eye, and spoke out the fateful words that changed my life, “I'll pay you five dollars if you eat those peas.”

    I only knew that five dollars was a huge, nearly unimaginable amount of money, and awful as peas were, only one plate of them stood between me and the possession of that five dollars. I began to force them down my throat.

    My mother looked livid (铁青色的). My grandmother had a self-satisfied look and said, “I can do what I want, Ellen, and you can't stop me.” My mother glared at her mother. She glared at me. No one can glare like my mother. If there were a glaring Olympics, she would undoubtedly win the gold medal.

    I, of course, kept shoving peas down my throat, and every single pea made me want to throw up, but the magical image of the five dollars floated before me, and I finally swallowed every last one of them. My grandmother handed me the five dollars with satisfaction. My mother continued to glare in silence.

    That night, at dinner, my mother served two of my all-time favorite foods, meatloaf and mashed potatoes. Along with them came a big, steaming bowl of peas. She offered me some peas, and of course I declined. My mother fixed me with a cold eye as she heaped（堆积) a huge pile of peas onto my plate. Then came the words that were to haunt (萦绕) me for years. “You ate them for money,” she said, “You can eat them for love.”

    Ms. O'grady, the head of Britains Trades Union Congress, issued a challenge on September 10th. "We can win a four-day working week, "she told members. The demand is far from new. Shorter working weeks have been tried in New Zealand and Sweden, wherein happier, healthier and more motivated employees. Those who work shorter weeks are also reported to be more productive. Should weekends, therefore, be lengthened?

    France's experience suggests workers may not leap at the chance of working for fewer hours. The government reduced the full-time workers week to 35 hours in 2000. Last year the French worked 38.9 hours a week on average, seeming happy to labor above the required level and pocket the extra pay or holiday allowance.

    And businesses may not seize the opportunity either. Working less may be linked to higher productivity (on a per-hour basis), but overall output could still fall because of the smaller number of hours worked. That will not get governments or employers excited.

    Advocates of a four-day week could claim that improving people's quality of life is more important than boosting the economy. In an essay published during The Great Depression, John Maynard Keynes wrote of an "age of leisure and abundance" in which technological advances would allow people to work 15-hour week.

    Unfortunately for any readers working hard on a Friday afternoon, Keynes jumped at his conclusion too soon. Even Ms. O'grady, now demanding a longer weekend, is pessimistic in her timescale. A four-day week is apparently achievable “in this century”.

DEAR Daughter,

    We have not seen you for a while now, so I thought we might check in. Did you fall off the edge of the Earth? Your mother worries, you know, and I am just curious. Well, I am more than curious. I feel abandoned.

    Apparently you've dumped us for your career. I can understand that, because you've always had a wonderful work ethic (道德).

    Look, obviously your long absence has confused us. As we go about our daily routines, your mother and I are distracted – both by your absence and our pride in your career. The other day, I entered my work password into the microwave, then stood there cursing it for not working. And I was so off my game (状态差) that I actually used that cholesterol-free mayo (不含胆固醇的蛋黄酱) your mother insisted on buying in an effort to drive me from the house.

    Listen, a lot has happened since you've been away. Abraham Lincoln was shot. We had two more children – a princess, now 23; a boy, now 12.

    Yesterday I bought a very clean 2001 Camaro car from an older woman. Your mother is not happy about this. She says it is the kind of muscle car driven by ex-convicts (有犯罪前科的人) when they examine your house at 2 am.

    In response, I tell her it was the car of my dreams (when I was 18). So that's where your long absence has left us. Your long absence is not so bad, though we miss your roaring laughter ... the way your cheeks flush (晕红) when you eat Thai food. How you always march too hard into the house, like a Scotsman stepping on snakes.

    Each evening, your mother now waits by the window the way she did when you used to step off the bus in first grade, your hair full of rubber bands.

    Bet that drove you crazy even then, her running out on the porch (门廊) like you'd just returned from a month-long journey to the moon.

    Look, parents are not easy people.

    But should the urge ever hit you, feel free to stop by some time. Our house is your house. Our hearts are yours too.

    And your mother is still waiting by the window.

Love,

Dad