Response of the neotenic salamander Haideotriton wallacei to a metamorphic agent.

The neotenic, cave-dwelling plethodontid salamander Haideotriton wallacei undergoes only a few minor integumentary changes and loses only a single bone, the coronoid, when treated with sodium laevo thyroxin. Since neither the animal's thyroid nor the supplementary thyroxin is sufficient to effect substantial metamorphosis, genetic factors probably restrict the animal's ability to transform.