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Histological studies of dental tissues will provide new and important insights into mammalian evolution. From studies of dental histology, hominoid evolution has become much clearer. Data as to the thickness of enamel and enamel prism patterns clearly provide quantitative support concerning theories of hominoid/hominid differentiation. The importance of comparative dental histology has only recently been realized and when extended to other mammalian orders, including both living and fossil forms, a more complete and clearer understanding of mammalian evolution will emerge. Caution must be emphasized, however, for these features are extremely complex structures and without a thorough knowledge of comparative dental histology and the applications of the SEM results may be misleading or incorrect.

Electrophysiological and behavioural methods have been applied to 34 species of the primates and, for comparison, to the Madagascan hedgehog to determine their responses to the proteins thaumatin and monellin. These substances elicit an intensely sweet taste sensation in man. All Catarrhina prefer monellin to water. The responses of the Prosimii as well as those of the South American primates to monellin are different, some species show a reaction, other species are not sensitive. In the case of thaumatin neither the Prosimii--including Tupaia and Tarsius--nor the South American primates show any response to this protein. Only the Cercopithecidae, the Hylobatidae and the Pongidae respond to this protein like man and prefer this substance to water. This physiological aspect of taste constitutes a clear dichotomy within the order Primates. This capability to taste thaumatin probably developed as long as 38 million years ago.

New phylogenies were recently proposed by White and Harris, who recognized 7 genera and 16 species of fossil and extant suids from sub-Saharan Africa. This scheme is regarded here as oversimplified and an alternative is suggested, in which 9 genera and 21 species are recognized. The taxonomic and phylogenetic differences do not have any significant effect on the stratigraphic interpretations offered by White and Harris.

Detailed study of a proximal fragment of a Pliocene left humerus and comparison with extant and fossil primates suggests that the specimen, although definitely hominoid, cannot be clearly associated with any known Plio-Pleistocene hominid or with any modern hominoids.

The combined properties of a given cutaneous system, like other characters classically employed by systematic zoologists, are useful criteria in the assessment of primate taxonomy and phylogeny. From the synthesis of all available data, it is also concluded that (1) the results define a baseline regarding the normal histology and histochemistry of the skin of most genera and many species of New World monkeys; (2) intrageneric and intraspecific subtleties in cutaneous variation exist in primate integument; (3) single and multiple cutaneous traits contribute to the characterization and accurate identification of most levels of taxa within the primate hierarchy; (4) some traits, however, negate recent taxonomic practices, e.g., the familial position of Callimico; (5) basic cutaneous patterns confirm currently accepted concepts of taxonomy and phylogeny; and (6) the various cutaneous signatures of extant platyrrhines record a history of adaptive radiation in isolation, and suggest that the designation of at least two distinct families is warranted.

The application of cladistic methods (especially a concentration on shared derived rather than ancestral characters) permits the distinction of four dental and two cranial morphocytes among the Cercopithecidae. Comparison with fossils suggests that the Fayum parapithecids are not specially related to the Old World monkeys, while other undoubted Fayum 'hominoids' may share derived features with monkeys. Miocene Victoriapithecus 'species' may document a stage very close to the split between Colobinae and Cercopithecinae. Later African colobines appear to form a monophyletic group, more arboreal than the extinct European branch; Asian forms may be specially related to the latter. Among the Cercopithecinae, after a Miocene separation from the high-forest Cercopithecini, the Papionini divided into three groups: geladas, sub-Saharan Papio-related 'baboons' and Mediterranean-Eurasian macaque relatives; each of these underwent Plio-Pleistocene adaptive radiations and subsequent taxonomic diminution.

Measurements were made of the cross-sectional area of neurons in the lateral geniculate nucleus (LGN) of normal monkeys, and of monkeys subjected to monocular and binocular eyelid suture. Early monocular deprivation caused a failure of normal cell growth in the LGN such that the neurons in the laminae innervated by the deprived eye were, on average, 15% smaller than those innervated by the normal eye. In the first 4 days of life monocular deprivation caused significant retardation of growth. The effect was marked in the first 6 weeks, but was not found in a monkey monocularly deprived from 11-16 months of age nor in an adult deprived for more than 6 months. Binocular deprivation from birth appeared to arrest neuronal growth at the neonatal size. The effect of monocular deprivation could be cancelled by 'reverse-suture' (opening the closed eye and closing the other) during the first 2 months of life. Changes in the size of LGN neurons following monocular deprivation and reverse-suture correlated closely with changes in the relative width of ocular dominance columns in layer IVc of area 17 of the visual cortex, measured physiologically in the same animals.

A new partial skeleton of an adult hominid from lower Bed I (about 1.8 Myr ago), Olduvai Gorge, is described. This specimen's craniodental anatomy indicates attribution to Homo habilis, but its postcranial anatomy, including small body size and relatively long arms, is strikingly similar to that of some early Australopithecus individuals.

We conducted karyological studies on one colony consisting of 12 Colombian and 34 Bolivian squirrel monkeys and a second colony of 47 monkeys imported into the United States between 1968 and 1974 through six importers. All animals in the first colony showed six acrocentric pairs of chromosomes. Bolivian monkeys were phenotypically distinguishable by their large size and coloration. In the second colony, 19 Peruvian, seven Colombian, five Bolivian and six Guyanan monkeys were correctly identified phenotypically and had five, six, six, and seven acrocentric pairs of chromosomes, respectively. Among Peruvian monkeys, 34.5% of the phenotypic classifications were in error.