Testicular follicles are descr. in certain female S. douthitti recovered from laboratory-reared, experimentally infected deer mice (Peromyscus maniculatus). Over 1350 stained female worms (650 from unisexual infections and 700 from bisexual) were examined, and testes were observed in 21 specimens aged 11 to 150 days. 18 hermaphrodites were from bisexual infections and 3 from unisexual infections. The testes in these worms lie posterior to the ovary, between the intestinal ceca; they vary in size and shape, have no efferent ducts, and all are immature. Except for testicular follicles, 11 of the 21 females appear normal. The remaining 10 possess abnormalities other than testes, such as decreased body-size, reduction in development of vitellaria and abnormal orientation of ovary. Factors favoring hermaphroditism in S. douthitti are not known.