Natural and experimental examples expand a word to the dimensions of a concept: instinct is first defined--"behavior that is inborn and does not have to be learned"; then its properties are refined--the term is descriptive but not fully explanatory. Internal stimuli (hormones) function chemically to prepare for a given action, and external stimuli trigger the action by exploiting, in the case of courtship for instance, the animal's best-developed sense (sight, sound, smell). His relative position on the evolutionary scale is what dictates the extent to which his innate or inherited 'outline' is filled in by 'learned' details. Word and picture portraits of particular species balance theory with a variety of intricate instinct-controlled behaviors: in courting, reproduction, and family-raising; in migration--the urge (glandular), navigation (sun- or star-oriented), and claiming of territory ("Is Man Territorial?"). However, "Instinct is too inflexible to cope with every situation that may arise. . . . Many species have become extinct because they were unable to adjust to changes in their environment"--here, discussion of genes, DNA, and mutation (re natural selection). Would-be observers are offered projects-in-context for inducing and conditioning instinctive reactions; further-readers will find a list of books (including juveniles) and accessible magazine articles for additional, delimited investigation. The authors know How Animals Learn (1969)--human animals--and they foster a sense of discovery.