American Scientist

To the Editors:

There is a simple answer to Brian Hayes's related questions: "How did the worm get to the center of the spiral without leaving an entry track?" and "What happened to the worm at the end of the track?" The worm was only one stage in the creature's development. The adult form laid an egg at the beginning of the track; the egg hatched, and the worm began its feeding. At the end of the track, the worm metamorphosed—perhaps into a free swimming form—and the process began again.

A similar life cycle is seen in a creature known as "subcutaneous larva migrans." Unsuspecting people can be affected on beaches in the Caribbean, where one or more eggs are laid under the skin of the beachgoer, usually on the buttocks. The larvae then migrate, leaving meandering tracks. The itch can be unbearable. The medical treatment is nauseating. I am not aware of the tracks ever intersecting themselves.

Manny Hillman
Blue Point, New York

Brian Hayes replies:

I am grateful to Manny Hillman for bringing to my attention this other kind of "bottomfeeder," and for omitting the nauseating details. The hypothesis that the worm's track begins with birth and ends with metamorphosis cannot be refuted, although one might wonder what became of the track of the egg-laying parent.