No. 2.] DEVELOPMENT OF BIDDER’S ORGAN. 461 
any tendency to the development of male organs by the fe- 
male in any of the Bufonidae. These facts are considered by 
Marshall (21) to furnish sufficient reason to overthrow the 
view that amphibians were originally hermaphroditic. In spite 
of the objections that can be brought against it, this theory 
seems to me to offer the most satisfactory explanation of the 
presence of Bidder’s organ in Bufo. It is conceded by most, 
1f not by all, zoologists that the spermatozoa are more highly 
differentiated than the ova. It is therefore only natural to 
suppose that in a degenerate sex-gland, such as Bidder’s 
organ, the germ-cells would follow in the course of their de- 
velopment the type of the least specialized germ-cells, the ova, 
rather than that of the more highly specialized spermatozoa. 
Such an organ would, therefore, have the same structure in 
all animals regardless of sex. According to this view it is 
only necessary to assume that Bidder’s organ has degenerated 
in the female more than it has in the male in order to have the 
conditions in this body what we find them at the present time. 
Since Bidder’s organ usually disappears in the adult female, 
although it persists throughout the lifetime of the male, there 
is good reason to believe that this body is more degenerate in 
the female than in the male. That the Bufonidae, which are 
among the most highly differentiated of the amphibians, 
should retain a primitive hermaphroditic condition of the gen- 
ital organs when such a condition 1s not found at the present 
time in other classes of amphibians, even among forms which 
are considered as primitive or degenerate types, is not an ob- 
stacle in the way of the theory outlined above. A some- 
what similar condition is found among certain fishes, and 
many of the higher vertebrates have retained primitive organs 
which are at present in a degenerate condition and seemingly 
of no use to the individual. 
Marshall has suggested that the formation of Bidder’s organ 
“may be regarded as due to a further extension backward of 
that tendency to degeneration and atrophy which has caused 
the conversion of the most anterior part of the germinal ridge 
into the fat body.” In accounting for the similarity in the 
