LAE STRUCTURE AND DEVELOPMENT "OF BLD- 
DER’S ORGAN IN BUFO LENTIGINOSUS. 
By HeEten DEAN KING. 
At the anterior end of the testis in all of the Bufonidae is 
the rounded body to which Spengel gave the name “Bid- 
der’s organ.” Although many of the investigators who have 
worked on the germ-cells of the Anura have examined this 
organ and ventured a conjecture as to its nature and probable 
function, Knappe (18) is the only one who has studied its 
development in any detail. In his paper, which appeared over 
twenty years ago, Knappe gives but a brief account of the 
early development of this body and he pays but little attention 
to the nuclear changes in the cells. Those who have more 
recently worked on Bidder’s organ believe, with Knappe, that 
this body is a rudimentary ovary, and they have been more 
interested in studying the maner in which the cells degenerate 
than in trying to determine the reasons for this degeneration. 
As an investigation of the nuclear and cytoplasmic changes oc- 
curring in the cells of Bidder’s organ during its early devel- 
opment might possibly give some clue to the function of this 
body and to the causes for the degenerative processes which 
occur in it, I have studied the structure and the formation of 
this organ in Bufo lentiginosus in connection with my other 
work on the germ-cells of this amphibian. Especial attention 
has been given in this study to the behavior of the chromatin 
and to the differences between the germ-cells in Bidder’s organ 
and those in the ovary which become functional eggs. For 
this investigation I have made use of material prepared for 
a study of the spermatogenesis and oogenesis of Bufo lentig- 
inosus. Methods of fixation and of staining are given in 
detail in preceding papers. . 
The formation of Bidder’s organ is first apparent when a 
tadpole is from fifteen to eighteen days old. Transverse sec- 
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