Fic. 1.—Portion of a transverse section through the middle of a tad- 
pole six days old. X 91. j 
Fic. 2—FPortion of a transverse section through the middle of a tad- 
pole nine days old showing the location of the germinal ridge. X QI. 
Fic. 3.—Section of the germinal ridge at the stage of Fig. 2. > 1,000. 
Fic. 4.—Section of the germinal ridge in a tadpole eleven days old. 
1,000. 
Fic. 5.—Transverse section of a divided germinal ridge in a tadpole 
thirteen days old. X 1,000. 
Fic. 6.—Longitudinal section showing the extent of the germinal 
ridge in a tadpole thirteen days old. XX 47. 
Fics. 7-9.—Sections through the germinal ridge in a tadpole fifteen 
days old showing the character of the cells at different levels. XX 1,334. 
Fic. 10.—Early prophase of mitosis in a primordial germ-cell. X 1,334. 
Fics. 11-12.—Equatorial plate in a primordial germ-cell. All 24 chro- 
mosomes are shown. XX 1,334. 
Fic. 13.—Longitudinal section of a spindle during the metaphase. Only 
5 of the chromosomes are shown. 1,334. 
Fic. 14—Late anaphase in a primordial germ-cell. XX 1,334. 
Fic. 15.—Section of the ovary at the time when sex is first apparent. 
Taken from a tadpole with very well-developed hind legs. > 1,000. 
Fic. 16.—Section of a young ovary showing the beginning of the 
formation of a central cavity. Taken from a tadpole about to undergo 
metamorphosis. > _ 1,000. 
Fic. 17.—Section of a young ovary containing a central cavity. Taken 
from a tadpole at the time of metamorphosis. X 1,000. 
