Mary Lou trudged despondently towards the science building. She didn't like days like she predicted this one would be. Prof. Bengston had warned them that their new experiment would be quite difficult as it would prove the chemical nature of inheritance. "Difficulty" usually meant her classmates would want to get her out of their hair, and that meant her part of the experiment was to be sent off to get doughnuts and drinks - and to keep the supplies frequently replenished - thanks to Jimmy's rapid consumption rate.

    Glory be! When she settled herself down in lab, early-bird Cheryl hadn't yet showed up. And that meant she would - at least until Cheryl arrived - be paired with handsome Jimmy, her secret heart-throb. What was more was that Bengston said that Jason and Wilbie had been invited to attend also for the first few minutes before they'd be sent off to work with Wilbie's uncle, Dr. Sørensen, a few blocks away at the Simplex Corp's lab there.

    After the high schoolers had been briefed on what they were to do at Simplex, the college students were left alone and given instructions as to how to turn some glass tubes about the diameter of large test tubes into U-shapes, and then how to fix sintered-glass filters down at the bottoms of the U's, thus dividing the two "horns" of each U into two equal compartments as shown to the right.

    Next they half filled each horn with fresh nutrient broth (like nutrient agar but without the agar). After covering the openings and sterilizing their U's, they inoculated one side of each with what they then called Streptococcus pneumoniae. All the while Mary Lou was delighted that the two of them were working so well together.

    Word then came in that Cheryl would not be attending lab for the next week as she was called away to a funeral for a grandparent. While this was sad, Mary Lou couldn't be happier at the prospect of having Jimmy all to herself for the whole week! She was beginning to like being involved in difficult lab work.

    After incubating the U's for 4 hours, they were then told to tip the tubes over 45° with the inoculated sides higher than the uninoculated sides. This would allow some of the upper parts to flow through the filters into the uninoculated sides. They were to check for growth in the lower sides the next morning.

    On the way out of lab, Jimmy actually told Mary Lou how nice it was working with her. "With Cheryl, I always feel uncomfortable and inadequate. I really look forward to working with you tomorrow." Needless to say, Mary Lou staggered home in a daze.

    The next morning, Mary Lou got up a bit early - surprising her family with her enthusiasm - spent a bit more time on her appearance, and then happily ran all the way to lab not wanting to miss a single moment with Jimmy.

    This is what each of their five U-tubes looked like:

    Prof. Bengston congratulated them on their perfect success, and Jimmy put his hand on Mary Lou's shoulder and said, "I couldn't have done it without my partner." Mary Lou's legs got weak, and she was sure her cheeks were blinking neon signs. For the next several hours, she could still feel where he had touched her shoulder.

    They cleaned out the tubes and re-half-filled them with nutrient broth, capped and sterilized them. Then Prof. Bengston produced two petri plates he said he had picked up that morning from Dr. Sørensen. The smaller colonies were capsule-deficient mutants derived from the normal, large-colony type. The plates looked like this:

    Jimmy told Mary Lou she should name the two types of Strep. pneumoniae, which she did. The left ones she called "Gummy" since the colonies were gummy and gelatinous, while the right ones she called "Dry" as they looked small, wrinkled and dried out.

    When their U-tubes had cooled, they were told to add drops of filter-sterilized enzymes to both horns of four of the tubes, and not to the fifth, since that would be their control. The enzymes were, in alphabetical order: amylase, DNase, protease and RNase.

    Next they were to inoculate the left-hand horns with "Gummies" and the right-hand sides with "Dried Out" cells, and incubate the tubes again on a 45° tilt so that the "Gummy" horns were on the upside.

    When they were done, Jimmy asked Mary Lou what she was doing after school because there was a movie he had wanted to see, but he didn't like seeing movies alone, and then even said he'd like to treat her to supper at the new Texan restaurant, the Frisky Bull. Mary Lou immediately had to sit down, but sighed on the way down, "I'd love to go with you."

    The next morning - a Saturday, they were to make streak plates from the "dry" (lower) horns of each tube. As that would take only moments, Mary Lou hoped they would have the whole day together. But what could they do? She really liked shopping at K-Mart and Wal*Mart, but she doubted that quarterback Jimmy would go for that. What to do?

    The plates were done, and Jimmy suggested that since the day was a bit on the warm side - actually due to get hot, they do something at the river. He said he had a pair of kayaks as well as a canoe. Mary Lou thought the canoe sounded more romantic, and so they stopped to pick up some picnic lunches and then to his house for the canoe, and spent a wonderful afternoon exploring before going out again to a restaurant for supper and then yet another movie. By this time Mary Lou couldn't remember all the places where Jimmy had touched her, and wondered the same about him.

    Monday came along. Mary Lou rolled out of bed to soon discover she could barely brush her hair as her arms and shoulders hurt so badly from the previous day's paddling. But she nevertheless had a smile and a spring in her step - even when she saw Cheryl had returned. Cheryl was in the corner with Bengston, who was explaining what had been done in her absence. Now came the big moment - and it wasn't what you might think! Jimmy told Cheryl that he wanted to work with Mary Lou, to which Cheryl rolled her eyes, but Mary Lou beamed at the thought that perhaps Cheryl would be sent on the eats run.

    Bengston brought out the plates, which appeared thusly:

    "Oh, the experiment didn't work!" exclaimed Cheryl.

    "Ah, but it did!" countered Mary Lou. "You just don't understand it," she continued rather smuggly.

    What momentous thing was discovered here?