Out of my head

I don't know why this is in my head, but it has been there for a long time, at least since high school:

I give you now Professor Twist,
The conscientious scientist.
Trustees exclaimed, "He never bungles,"
And sent him off to distant jungles.
Camped on a tropic riverside,
One day he missed his loving bride.
She had, the guide informed him later,
Been eaten by an alligator.
Professor Twist could not but smile.
"You mean," he said, "a crocodile."