354 The Spermatogenesis of Bufo Lentiginosus 
nucleus continues until all of the chromatin is collected in an oval or 
spherical mass lying usually close to the nuclear membrane with which 
it is connected by very fine fibres (Figs. 21, 22). In preparations stained 
with iron-hematoxylin in the usual manner this mass of chromatin ap- 
pears perfectly black and apparently homogeneous (Fig. 22) ; if, however, 
the greater part of the stain is extracted from the sections, this structure 
is found to be composed of a tangled mass of very fine, granular filaments 
among which are a number of rounded, deeply staining nucleoli (Fig. 
23). These nucleoli, judging from their staining reactions, are not 
plasmosomes, but more condensed portions of the chromatin substance 
which retain the hematoxylin with great tenacity. 
It can readily be demonstrated that this condensation of the nuclear 
contents is an actual constructive stage in the normal course of the 
development of the spermatocytes of Bufo and is not “ the expression of 
a running out in the spermatogonium stock and represents a tendency 
towards degeneration,” as claimed by Kingsbury (29) for Desmognathus. 
In the testes of adult toads killed at any time during the summer 
months, large numbers of spermatocytes can be found showing every 
step in this process from the stage shown in Fig. 16 to that of Fig. 
22, no matter what method of fixation or of staining has been employed. 
In the testes of toads killed in September and October, the maturation 
divisions are rarely found, and most of the cysts are filled with sperma- 
tids and maturing spermatozoa. If the spermatocytes in which a con- 
densation of the nuclear contents occurs during the summer months are 
in a state of degeneration, one would expect to find the testes of toads 
killed in the autumn filled with a large number of cells in the process 
of disintegration; but such is not the case. It seems quite improbable 
that large numbers of cells could disintegrate and the débris be disposed 
of so quickly that it is impossible to obtain any late stages in the 
process. 
I have never found a condensation of the chromatin in the spermato- 
gonia as Kingsbury has described for Desmognathus, and I am unable 
to confirm his statement that “ contraction figures do not occur con- 
stantly in spermatocytes.” In Bufo the synizesis stage is most frequently 
met with in the testes of toads killed in the early summer months simply 
because at this time the testes contain relatively more cells in this par- 
ticular stage of development. Contraction figures are, however, to be 
found in practically any section of the testis, no matter what time of 
year the toad is killed, and they are found in relatively the same abund- 
ance in the testes of young toads as they are in the adult. 
