The development and morphology of the gonads of the mouse.— Part I. The morphogenesis of the indifferent gonad and of the ovary

Abstract

A table of 9 stages showing distribution of extra-regional germ cells and stages of development of gonads is given. First traces of the germinal ridge were found in 9-day post-coitus embryo. The ridge became a solid mass of epithelium. The testes differentiated 111/2-12 days p.c. A downgrowth of connective tissue from the hilum formed a tunica albuginea and broke the epithelial mass into spermatic cords. The ovaries remained indifferent after the testes had differentiated and the epithelial mass remained solid. The epithelium of the ovary proliferated until the 4th or 5th week post partum. It was not divided into medullary, cortical and definitive proliferations as in the cat. Mesenchyme growing down from the hilum established the tunica albuginea and septa ovarii in 16 days p.c. The medulla was formed by connective tissue from the hilum when the deeper germ cells were degenerating. Degenerating oocytes were found at all stages after the differentiation of the ovary. After birth many follicles grew precociously and degenerated about weaning time. Sex could be distinguished easily microscopically at 121/2 days p.c. Primordial germ cells came from the germinal epithelium; some became extra-regional germ cells. No germ cells showing synaptic stages were found in stages more than 4 days old.- H. F. Nachtrieb.