Helen Dean King 355 
From a study of the spermatogenesis of Batracoseps attenuatus Jans- 
sens (24) concludes that a condensation of the nuclear contents occurs 
only when material is badly preserved, and he states that cells of this 
type are commonly met with in the central mass of tissue where the 
reagents have not penetrated sufficiently well. Such an explanation will 
uot account for the presence of synizesis in the spermatocytes of Bufo. 
Cells in this stage of development are found as frequently in the cysts 
at the periphery of the testis as in those at the centre, and not infrequently 
a cyst filled with spermatocytes in the synizesis stage les adjacent to a 
cyst containing dividing cells in which the chromosomes, centrosomes, 
and achromatic structures are remarkably clear and well preserved. I 
do not think it possible that a method of fixation that would cause the 
nuclear contents of one set of cells to become as contracted as that 
shown in Fig. 22, would not also distort the contents of the other cells 
of the surrounding tissue to a greater or a less degree. 
In none of the amphibians that have so far been studied is the con- 
densation of the chromatin in the primary spermatocytes as complete 
as in the case of Bufo. Janssens (23) states that in the resting stages 
of the spermatocytes of Triton all of the substance of the nucleus is 
collected in a mass from which numerous filaments extend out to various 
parts of the nuclear membrane. The synizesis stage in Triton is, accord- 
ing to Janssens, about like the stage of condensation in Bufo shown in 
Fig. 20. In Salamandra, Amphiuma, Batracoseps, and Plethodon, ac- 
cording to the investigators who have worked on these amphibians, there 
is no stage in the development of the spermatocytes in which a condensa- 
tion of the nuclear contents occurs. The spireme formed after the 
last spermatogonial division splits longitudinally at a stage about like that 
of my Fig. 15, and it subsequently breaks into the reduced number of 
chromosomes. If a condensation of the nuclear contents of the sperm- 
atocytes is not characteristic of these cells in all amphibians, it certainly 
is not confined to Bufo and Triton as I have already found it in several 
species of Rana and in two of the Urodela. 
It is obviously impossible to determine what changes are taking place 
in the chromatin during the time that the substance of the nucleus is 
massed together in the synizesis stage, as no definite structures, other 
than those shown in Fig. 23, can be made out even in the most favorable 
preparations. Judging from the results that have been obtained from a 
study of the spermatocytes in other species in which a condensation of 
the chromatin does not occur, it is probable that during synizesis the 
chromosomes become united end to end in a spireme which later seg- 
