ABSTRACT
Animal behaviour shows almost as much differentiation as does either animal morphology or physiology. Among the Primates differentiation of this kind is easily observed, and its taxonomic implications are in close harmony with classification based on external characters. The nose and upper lip of animals belonging to the sub-order Lemuroidea are constructed differently from those of higher Primates, and in their structure they represent the primitive mammalian naked glandular rhinarium. The distinction between the three sub-orders of Primates is well defined in the matter of facial expression. Exhibiting the teeth in a wide yawn in moments of dominance preceding fights—a movement which may justifiably be interpreted as a threatening one—is another expression common to apparently all the catarrhine Primates. The activities comprising grooming behaviour differ considerably amongst the Primates. The examples of behaviour patterns demonstrate clearly the differentiation of the main groups of Primates.
