No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 379 
apparently multinucleated cells are not preparing to divide by 
amitosis. Their appearance is doubtless due to the fact that 
in sectioning the cells the polymorphic nuclei were cut in such 
a way as to completely separate two or more lobes. In my 
study of the germ-cells of Bufo I have never found a single 
instance where I could be sure that a cell was dividing amitoti- 
cally; and I am convinced that this mode of division does not 
normally occur in any of the germ-cells of the ovary or of the 
testis. 
By the time that a tadpole is sixteen to eighteen days old 
the anterior portion of each genital ridge has developed into 
a small rounded body, the so-called “Bidder’s organ.” The 
structure and development of this organ will form the subject 
of a separate paper and therefore no further mention of it 
will be made here, as it has seemingly nothing to do with the 
development of the ova. 
Although sex is doubtless determined at a very early stage 
of development, the germ-cells of Bufo remain in an apparently 
indifferent condition for a long period, and it is not until 
the tadpole is about to undergo metamorphosis that its sex 
can be ascertained with any degree of certainty. Several 
investigators of amphibian odgenesis have stated that the 
presence of a central cavity in the genital ridge is the first 
characteristic by which the young ovary can be identified. In 
Bufo it is possible to distinguish the sexes at a somewhat 
earlier period of development by means of the arrangement 
of the cells in the more anterior portion of the sex-gland. In 
the young male the germ-cells are scattered evenly through- 
out the testis, each being surrounded by a number of follicle 
cells; in the young female the germ-cells have a definite ar- 
rangement around the outside of the ovary, while the centre 
is filled with peritoneal cells (Fig. 15). There -is no central 
cavity in any part of the genital ridge at this time. 
When the genital ridge has taken on the definite character 
of an ovary, some of the odgonia still contain a few small yolk 
spherules (Fig. 15), although all traces of yolk have long 
since disappeared from the other cells of the body. There is 
no ovarian wall at this time and the odgonia are surrounded 
