No. 2.] DEVELOPMENT OF BIDDER’S ORGAN. 455 
18. There is the possibility, however, that it may be caused 
by currents in the cytoplasm of the degenerating eggs which 
separate the more fluid portion of the cytoplasm from the 
more granular, as is sometimes the case in the cells of Bid- 
der’s organ. 
The degenerative changes taking place in the cells of Bid- 
der’s organ are very similar to those which occur in mature 
amphibian eggs which have remained in the ovary after the 
breeding season, according to the investigations of Bihler (4), 
Dubnisson (10), Ruge (28), and others. In such eggs the 
chromatin breaks up into granules and, after the disappear- 
ance of the nuclear membrane, the substance of the nucleus 
mingles with that of the cytoplasm, the egg being finally ab- 
sorbed through the agency of follicle cells, leucocytes and blood 
capillaries which have penetrated into the cytoplasm. Eggs 
which are degenerating in the ovary are always heavily pig- 
mented, however, while pigment is rarely developed in the 
cells of Bidder’s organ and when it is present it never seems 
to be concerned in the degenerative processes. 
Bidder’s organ is a permanent structure in the males of 
all species of the Bufonidae so far investigated. In Bufo 
variabilis, Bufo cinereus, and Bufo calamita, this body dis- 
appears in the female at the end of the second year. In Bufo 
vulgaris, according to the observations of Knappe, Bidder’s 
organ disappears in the adult female during the winter and a 
new organ is regenerated during the summer months. Ac- 
cording to Ognew, Bidder’s organ does not disappear in the 
adult female of Bufo vulgaris during the winter, but it per- 
sists as a small shrunken organ which lies near the fat bodies. 
Bufo vulgaris is, therefore, the only species so far studied in 
which Bidder’s organ is a permanent structure in both male 
and female. 
In Bufo lentiginosus Bidder’s organ disappears in the female 
at the end of the second year and no traces of it are to be 
found in older females. During its early development this 
organ contains no central cavity, although there are a number 
of intercellular spaces between the rounded ova. After the 
