EXPLANATION OF PLATES. 
All figures were drawn with the aid of a camera lucida. They have 
been reduced one-third. 
Fic. 1.—Outline drawing of the genital organs of a toad killed at the 
time of metamorphosis. C. A., corpus adiposum; B. O., Bidder’s organ; 
O., ovary; R., kidneys. 
Fic. 2—Section of Bidder’s organ taken from a tadpole 17 days old. 
X_ 1,000. 
Fic. 3.—Section of Bidder’s organ taken from a tadpole 35 days old. 
<_ 1,000. 
Fic. 4.—Resting stage of a primordial germ-cell in Bidder’s organ. 
V., vitelline bodies. XX 1,334. 
Fic. 5.—Young oocyte in Bidder’s organ. X 1,334. 
Fic. 6.—Growth stage of a young oocyte. X1I,334. 
Fic. 7—Beginning of the condensation of the chromatin spireme lead- 
ing to synizesis. X 1,334. 
Fic. 8—Synizesis stage. X 1,334. 
Fics. 9-10.—Early post-synizesis stages. The chromatin is in the form 
of a continuous spireme. XX 1,334. 
Fics. 11-14.—Post-synizesis stages showing the division of the spireme 
into segments. XX 1,334. 
Fic. 15—The beginning of amitotic division in the nucleus of a cell 
in Bidder’s organ. X 1,334. 
Fics. 16, 17.—Later stages in the amitotic division of a cell. X 1,000. 
Fic. 18.—Section of an odcyte which has begun to degenerate. A fluid 
space has formed around the large nucleolus and the yolk material is col- 
lected in several masses, one of which lies against the nucleus. XX _ 1,000. 
Fic. 19.—Section of an egg in Bidder’s organ taken from a toad killed 
at the time of metamorphosis.. Yolk-nuclei are forming in the cytoplasm. 
>< 4.000! 
Fic. 20.—Section of the nucleus of a cell in Bidder’s organ which 1s 
very similar to nuclei of the same size found in the ovarian odcytes. X 
1,000. 
Fics. 21-25.—Stages in the resolution of compound-nucleoli in the cells 
of Bidder’s organ. X 1,334. 
