Ameba (Gr. amoibē, change), a primitive single-celled animal.
Amphibian (Gr. amphi, both; bios, life), capable of living both on land and in water.
Anthropoid (Gr. anthropos, man; eidos, form), man-like.
Aristogenic (Gr. aristos, best; genesis, origin), pertaining to the genetically most desirable human strains.
Association Areas, those regions of the brain in which presumably the higher mental processes are effected.
Atavism (L. ad, before; avus, grandfather), a return in one or more characters to an ancestral type. See [p. 8] for restricted modern usage.
Atrophy (Gr. a, negative; trophē, nourishment), a wasting away of a part of a living organism.
Axon (Gr. axon, axis), the process from a nerve cell which becomes a nerve fiber.
Binet-Simon Scale, a series of tests graded to age and previous training of the average normal child, much used in measuring mental deficiency.