34O A. RICHARDS AND JAMES T. THOMPSON. 



King, H. D. 



'08 The Oogenesis of Bufo Lentiginosus. Jcur. of Morphology, Vol. 19 



P- 369. 

 Nussbaum, M. 



'80 Zur Differenzierung des Geschlechts im Tierreich. Arch. f. mikr. Anat., 



Bd. 18. 

 Swift, C. H. 



'14 Origin and Early History of the Primordial Germ-Cells in the Chick. 



Amer. Jour, of Anatomy, Vol. 15, No. 4. 



'15 Origin of the Definitive Sex-Cells in the Female Chick and their Rela- 

 tion to the Primordial Germ-Cells. Amer. Jour. Anat., Vol. 1 8, p. 441. 

 '16 Origin of the Sex-Cords and Definitive Spermatogonia in the Male 



Chick. Amer. Jour. Anatomy, Vol. 20, p. 375. 

 Wilson, H. V. 



'89 Embryology of the Sea Bass. Bull. U. S. Fish Comm., Vol. 9. 

 Woods, F. A. 



'02 Origin and Migration of the Germ-Cells in Acanthias. Amer. Jour 

 Anat., Vol. i, No. 3. 



EXPLANATION OF ILLUSTRATIONS. ' 



All figures in this report were drawn with the aid of a camera lucida. 

 Any lens combinations which were considered necessary to produce the best 

 results were used. The magnification as given for each figure was calculated 

 carefully and is correct for the reproductions as they appear on these plates. 



ABBREVIATIONS. 



a., anus. Mes., gut mesentery. 



Ao., aorta. Af, notochord. 



B., blood cells. Nt., neural tube. 



c., centrosome. nu., nucleolus. 



cr., chromatin knots. P., peritoneum. 



Co., ccelome. pe., periblast. 



Ect., ectoderm. P.N., periblast nucleus. 



EM., endodermal cell mass. 5"., sex-cell. 



En., gut endoderm. sw., swim bladder. 



G., germ gland anlagen. So., somatic mesoderm. 



g. t gut. Sp., splanchnic mesoderm 



L.M., lateral mesoderm. T., elongating tail. 



li., linin network. Wo., Wolffian duct. 



M., mesoderm. 



