No. 2.] DEVELOPMENT OF BIDDER’S ORGAN. 441 
organ increase in number after a certain period in the devel- 
opment of this organ, but the cells so dividing are not capable 
of becoming functional eggs. In Bufo, amitosis in the germ- 
cells is undoubtedly correlated with degeneration since the 
germ-cells which become functional always divide by mitosis 
(King, 16). 
Hoffmann (14) is, I believe, the only investigator who has 
found the cells of Bidder’s organ dividing by mitosis. Knappe 
states that from the beginning the increase in the number of 
cells in this organ is solely through amitosis. In tadpoles of 
Bufo lentiginosus it ts possible to find amitosis and mitosis oc- 
curring simultaneously in Bidder’s organ (Fig. 3, A and Y), 
but a cell dividing amitotically is always older than one divid- 
ing by mitosis, since the nucleus of a cell has to undergo a 
definite series of changes before amitosis occurs. After a cell 
has once divided directly it is not capable of again dividing 
by mitosis. 
The resting germ-cells in Bidder’s organ appear similar to 
the resting germ-cells in the sex-gland, as they.are large 
round or oval cells with polymorphic nuclei which contain a 
faintly staining granular reticulum and several nucleoli (Cf. 
Fig. 4, Plate V and Fig. 18, Plate IL). Owing doubtless to 
the rapid growth of Bidder’s organ the yolk spherules disap- 
pear from its cells much sooner than from the cells of the sex- 
gland, and they are rarely to be found in the anterior part of 
the genital ridge after the tadpole has attained a length of 
7-8 mm. When the yolk has disappeared the cytoplasm of 
the germ-cells appears granular, and it is found to contain 
one or two vitelline bodies (Fig. 4, V) and a centrosome (Fig. 
3, C). At this stage of development there is nothing to indi- 
cate that these cells differ in any way from the germ-cells 
in the other portions of the genital ridge. 
After the last mitotic division the cells take on the character 
of young odcytes and they usually have several peritoneal cells 
flattened against their outer surface (Cf. Fig. 5, Plate V and 
Fig. 21, Plate II). The nucleus of the cell is no longer poly- 
morphic but rounded in outline and it contains a faintly stain- 
