The Mexican axolotl (Ambystoma mexicanum) is an animal of great value to developmental biology because it has the ability to regenerate certain body parts, such as its limbs (Thornton, 1968), and has within its genome a number of developmental mutants (Briggs, 1969; Humphrey, 1972). It is therefore of interest to seek methods that will increase the frequency of fertile spawnings of this animal. The two methods most commonly used to achieve axolotl spawnings have been described in detail by Humphrey (1962). Briefly, one of these procedures is simply the placing of a sexually mature female together with a sexually mature male into a properly prepared aquarium overnight. If mating is successful, the behaviour that results stimulates spermatophore release by the male followed by insemination of the female, which then ovulates and subsequently spawns. The problem with this method is that only one in several mating attempts results in a spawning.