160 Helen Dean King. 
indifferent state even at the time of metamorphosis, and in many 
instances the genital glands must be examined histologically before 
the sex of an individual can be ascertained. The toad grows very 
rapidly after completing its metamorphosis, and then, except in very 
rare cases, the sexes are readily distinguished by an examination of 
the sex-glands under a dissecting lens. At this period of development 
the testes are long, cylindrical bodies with a smooth contour (Figs. 3 
and 6, Left) ; the ovaries, although they are of about the same length 
as the testes, are relatively broader and they have an irregular, jagged 
outline (Figs. 5 and 7, Left). At the anterior end of each genital 
gland is a large rounded body, Bidder’s organ (Fig. 1, B. O.), to 
which the corpora adiposa are attached (Fig. 1, C. A.). In young 
toads Bidder’s organ is of the same size and structure in both sexes: 
it persists throughout the lifetime of the male, but it disappears in 
the female towards the end of the second year. <A study of the struc- 
ture and development of Bidder’s organ (King, ’08 a) has shown that 
this body is undoubtedly a rudimentary ovary in which the cells have 
marked characteristics which readily distinguish them from the eggs 
developing in the ovaries. 
As a rule there is but one Bidder’s organ at the anterior end of a 
sex-gland, and it usually measures about 0.4 mm. in diameter. In 
many young toads Bidder’s organ shows considerable deviation from 
the normal size and shape. In some instances this structure is very 
large, measuring 0.6 mm. in diameter (Figs. 1, 2, 7); in rarer cases 
it is less than one-half of its usual volume (Fig. 13). Examined 
histologically such Bidder’s organs are found to differ from those of 
normal size only in the number of ova that they contain. 
Not infrequently a Bidder’s organ is found that is greatly elon- 
gated (Figs. 7,9, 12). In such eases this body is usually indented in 
the middle region (Figs. 7, 9), although sometimes it has a perfectly 
smooth contour (Fig. 12). Anomalies of this kind indicate clearly 
the steps by which the one Bidder’s organ becomes divided into two; 
and the presence of two of these structures at the anterior end of an 
ovary or of a testis is probably the most common abnormality occur- 
ring in the genital organs of young toads. Usually, in cases like this, 
one Bidder’s organ lies directly behind the other (Figs. 1, 10, 11, 
