346 The Spermatogenesis of Bufo Lentiginosus 
a course of development similar to that of the spermatozoa which are 
first formed in the young. 
The testes of the adult toad are cylindrical bodies lying directly in 
front of the kidneys. They measure from 10 mm. to 12 mm. in length 
and from 2 mm. to 3 mm. in width, the difference in size depending 
doubtless on the age of the toad. At the anterior end of each testis, and 
continuous with it, is a small, rounded structure, the so-called “ Bidder’s 
organ.” This body is probably a rudimentary ovary, as several investi- 
gators have maintained, and it has seemingly nothing to do with the 
development of the spermatozoa. 
Kach testis is divided into a number of compartments, or follicles, 
separated by comparatively thick walls which contain numerous follicle 
cells. Each follicle is, in turn, divided into several smaller compart- 
ments, or cysts, which are separated from each other by much thinner 
walls. As a rule, all of the cells in a cyst are in approximately the 
same stage of development; but a single follicle may contain both 
spermatogonia and maturing spermatids. A transverse section of the 
testis, therefore, shows practically all stages in the development of the 
spermatozoa. As might be expected, testes of adult toads killed soon after 
the end of the breeding season contain large numbers of dividing sperm- 
atogonia; while the testes of toads killed in August or September con- 
tain relatively more spermatocytes and spermatids. 
The structure of the testis of a young toad is similar to that of the 
adult except that there are fewer follicles and cysts. Until the toad has 
attained a body length of about 2 cm. the testes contain nothing but 
spermatogonia surrounded by follicle cells. After this time some of the 
cells evidently develop much faster than others, as spermatids can always 
be found among the spermatogonia and spermatocytes in the testes of 
toads 3 cm.Jong. When the young toad is about 5 cm. in length sections 
of the testes, except for their smaller size, cannot be distinguished from 
those of an adult killed in the early autumn. 
Various fluids were used for fixation of the material, by far the most 
satisfactory being Flemming’s solution (strong formula). Corrosive- 
acetic, which gives exceedingly good preparations of the egg, is but an 
indifferent fixing fluid for the testes as is also Gilson’s mercuro-nitric 
solution. As a rule, the sections were stained with Heidenhain’s iron- 
hematoxylin which was followed by erythrosin or orange G. Such a 
combination stain seems to differentiate the achromatic structures of 
the cell, particularly the attraction-sphere and the centrosome, as sharply 
as it does the chromatin. Safranin followed by lichtgriin and Her- 
