460 KING. [Vor. XIX. 
of the development of this structure point to the same con- 
clusion. The germ-cells of Bidder’s organ arise from primor- 
dial germ-cells which are similar in character to the cells 
which become functional spermatozoa or eggs, and the early 
development of these cells closely follows that of the ovarian 
ova up to the synizesis stage. During synizesis the cells of 
Bidder’s organ appear similar to spermatocytes in which the 
nuclear contents are in a contracted condition, but at no other 
period in their development do they resemble in any way 
stages in the development of the spermatozoa; neither are 
they similar to any cells of the body except the ova. Even 
when the cells of Bidder’s organ are degenerating their re- 
semblance to the ovarian ova is very marked, and the degen- 
erative processes occurring in them are similar to those taking 
place in the mature eggs which are not expelled from the ovary. 
There is, therefore, no probability that Bidder’s organ is a 
portion of the testis which has been arrested in its develop- 
ment to serve as an accessory male organ as Bidder, Leydig, 
and Spengel maintain. 
If Bidder’s organ is a rudimentary ovary there are three 
possibilities that may be considered in a discussion of the 
origin of this body. It is possible, as Haeckel (13) suggests, 
“dass das alteste und ursprtinglichste Geschlechtsverhaltniss 
die Zwitterbildung war und dass aus dieser erst secundar 
(durch Arbeitstheilung) die Geschlechtstrennung hervorging.”’ 
This primitive hermaphroditic condition has been lost by most 
of the vertebrates, although it still persists in many of the 
lower forms. If the amphibians were originally hermaphro- 
dites then this primitive condition of the sex-glands still ex- 
ists in the Bufonidae, being indicated by the presence of Bid- 
der’s organ. On this assumption Bidder’s organ is a degen- 
erate ovary in the male toad and a degenerate testis in the 
female. 
In the female toad the cells of Bidder’s organ have no re- 
semblance whatever to the sperm-cells and in their structure 
and development they resemble the ovarian ova as closely as 
do the cells of the Bidder’s organ in the male; neither is there 
