cute joke found on a biology website

There was a biology student who was studying equilibrium in sea birds with a
specific focus on terns. He proposed that giving measured doses of THC (from,
of course, marijuana) and observing their flight patterns would give some
insight to the problems of equilibrium in three dimensional space. This
proposal being given in a more liberal era, the student got the funding. He
filled out mountains of forms, set up a lab with a ready supply of terns, and
proceeded on his way. After a year of diligent work, groveling monthly before
the review committee to get his stipend, and living with drugged terns, he
completed his study.

With trembling hands, he delivered his 247-page report, complete with charts
and graphs, to the review committee. The august body peruses his study, asking
penetrating questions and reducing our student to jell-o. Finally, the
department head rises. The light reflects off her steel rimmed glasses as she
stares down at our student.

"There is a lot of good work here," she says. "But we can't accept this report.
You have detailed marvelously the effects of THC on terns but you forgot one
essential step: you have no control group." Our student turns pale and says,
"You don't mean..."

"Yes. I'm afraid so. You left no tern unstoned."