Varicella virus appears to be extremely species specific and apart from man evidence of infection has been found only in vervet and green monkeys (Cercopithecus lalandi and sabaeus). Rivers (1926, 1927) inoculated young males of both species intratesticularly with emulsified vesicles and papules collected within 48 to 72 hours of the onset of the rash in chickenpox. In these animals spermatogenesis had not been initiated and he found intranuclear inclusions in cells in regions of the testes damaged by the inoculation. These inclusions were demonstrable 5 or 6 days after inoculation but not later than this (Rivers, 1926). Subsequently (Rivers, 1927), it was shown that intranuclear inclusions were not formed if the inoculum was mixed with convalescent-phase (14 to 21 days) chickenpox serum before it was injected, although the same material mixed with acutephase (3 days or less) serum still produced inclusions. Monkeys immunized by previous injections of varicella virus also failed to develop intranuclear inclusions on subsequent intratesticular inoculation.