Abstract
The testes of 81 Himalayan rabbits, controls in toxicity studies, and 113 purpose-bred rabbits of various age groups from birth to 2 years were studied. In mature male rabbits, regressive changes in the seminiferous tubules including the multinucleated spermatid giant cells were common and showed a tendency for age-related and seasonal differences. The finding is considered as a remnant of the previous seasonal and possibly also social testicular regression in wild living animals. The giant cells develop from the syncytium of the germinative epithelium and have parallels in phylogenesis.