Phytohemagglutinin causes cultured lymphocytes to agglutinate, divide, and produce gamma-globulin. Most cells are transformed into large lymphocytes, some resembling plasmocytes. Actinomycin D stops gamma-globulin production after 2 hours. When specific antigens are added to lymphocytes from sensitized individuals, only some cells undergo morphological transformation, produce gamma-globulin, and divide. When cells or cell extracts from an unrelated individual are added to a culture, a similar reaction occurs.

Metaphase chromosome preparations of three male and one female Gorilla gorilla were stained to demonstrate quinacrine, Giemsa, centromeric heterochromatin, and, in one case, reverse-Giemsa bands. A standard karyotype is proposed based on chromosome banding pattern, centromeric index, and length. Three types of variation between homologous chromosomes are described: presence or absence of very bright fluorescence of the short arm or satellite region of acrocentric chromosomes, presence or absence of bright quinacrine bands at the distal ends of chromosome arms, and large differences in the size of the heterochromatic region on each of two biarmed chromosomes. At least half the chromosome pairs show polymorphisms of these types. Satellite associations were scored for each animal. In one case the two smallest pairs of chromosomes were preferentially involved in associations.

A standard nomenclature for chimpanzee chromosomes is proposed, based on banding patterns and measurements. Comparison of chromosome lengths suggests that the total amount of chromosome material is approximately the same in the human and chimpanzee. Correlation of banding patterns and measurements confirm that the chromosomes of the two species differ by rearrangement of heterochromatic material, several pericentric inversions, and at least one translocation.

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