No. 2.] DEVELOPMENT OF BIDDER’S ORGAN. 459 
and Spengel (31, 32) also consider that Bidder’s organ is an 
accessory organ and not an ovary. ‘The latter investigator 
thinks it highly probable that “dies Organ eine Rolle in den 
Leistungen der Geschlechtsdrtisen, spielt, etwa in irgend einer 
Beziehung steht zur Bildung des Materials von der die Ent- 
wickelung neuer Ureier ausgeht, im weiblichen wie 1m mann- 
lichen Geschlechte.”’ 
Spengel gives three reasons why he does not believe that 
Bidder’s organ is a rudimentary ovary: (1) the anatomical 
differences between Bidder’s organ and the true ovary consist- 
ing in a lack of a central cavity in Bidder’s organ and the ab- 
sence of pigment and yolk from the cells themselves; (2) the 
fact that Bidder’s organ is found in the female as well as in 
the male; (3) the presence of Bidder’s organ in hermaphro- 
ditic toads. Later researches have rendered the first of these 
reasons invalid since Bidder’s organ has been found to con- 
tain a central cavity. Knappe has found pigment in the cells 
of Bidder’s organ in Bufo vulgaris, and I have also found 
it in Bufo lentiginosus. The formation of yolk-nuclei is a com- 
mon phenomenon in the cells of Bidder’s organ in tadpoles of 
Bufo lentiginosus, and in one instance (Fig. 26) I have found 
the cells of Bidder’s organ developing yolk spherules. AlI- 
though Bidder’s organ was found in the hermaphroditic toad 
examined by Spengel it is not present in a most interesting 
specimen of Bufo vulgaris recently described by Cerruti (7). 
In this individual there is a well developed testis in front of 
each kidney, and lying between each testis and the fat body is 
an ovary which appears to be intermediate in structure between 
a true ovary and Bidder’s organ. In this individual Bidder’s 
organ has been able to develop further than it normally does 
and it has thus become a part of the rudimentary ovary. This 
development would probably not have been possible if Bid- 
der’s organ were merely an accessory male organ. 
The evidence brought forward by the investigators who 
have more recently studied the structure of Bidder’s organ 
in adult toads has been unanimously in favor of the view that 
this body is a rudimentary ovary, and the results of my study 
