No. 2.] DEVELOPMENT OF BIDDER’S ORGAN. 457 
organ is increasing in size. My study of the spermatogenesis 
of Bufo lentiginosus (King, 16) has shown that early summer 
is the time when the sperm-cells are most actively dividing 
and that in August and September, when large numbers of 
the cells of Bidder’s organ are beginning to degenerate, the 
testes are filled with spermatids and spermatozoa. The growth 
of Bidder’s organ is therefore most rapid during the period 
when the cells of the testis are most actively developing into 
spermatozoa. The degeneration of numerous cells of Bidder’s 
organ at the end of the summer is not due to the beginning 
of a period of sexual activity on the part of the testes, but to 
the fact that these cells have reached their maximum stage of 
development and, since they can go no further, they must of 
necessity degenerate. During the winter there is no active 
formation of new cells in Bidder’s organ, and many of the 
cells already formed gradually reach their maximum develop- 
ment and then disintegrate. In the spring, therefore, Bidder’s 
organ is only about one-half of its former size. New cells 
are formed in great numbers in Bidder’s organ only at the 
time that new cells are developing in the testes. 
In adult males the nuclei of the cells of Bidder’s organ 
usually contain a number of small nucleoli rather than one or 
two large ones as is so often the case in the young animals. 
The cytoplasm of these cells usually appears uniformly granu- 
lar until it is beginning to be absorbed by the follicle cells and 
by the leucocytes. Yolk-nuclei are very rarely developed in 
these cells, and when they are found they always appear like 
the granular masses shown in Fig. 18. Disintegration of the 
cells through the agency of blood capillaries which have pen- 
etrated into the cytoplasm occurs much more frequently in the 
Bidder’s organ in the adult than in the young toad. 
Investigations have shown that Bidder’s organ is not found 
in the amphibians as a class, but that it is confined to the 
Bufonidae except in rare instances. In 1830, Muller (22) 
stated that a rounded body is present at the anterior end of 
the testes in tadpoles of Pelobates fusca and also in those of 
Rana. These observations have not been confirmed by other 
