In the normal development of the sparrow testis, a daily period of active spermatogenesis is found between the hours of 2:00 A.M. and 4:00 A.M. This restriction to the hours of darkness appears all the more significant since an inversion of the light period results in the occurrence of mitotic figures during the afternoon hours.
Proceedings of the Iowa Academy of Science
©1936 Iowa Academy of Science, Inc.
Riley, Gardner M.
"Factors Controlling the Diurnal Spermatogenic Cycle of the Male Sparrow (Passer domesticus),"
Proceedings of the Iowa Academy of Science, 43(1), 396-397.
Available at: https://scholarworks.uni.edu/pias/vol43/iss1/147