No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 385 
elasmobranchs. The latter investigator states that “some of 
the nuclei of each nest are converted into the nuclei of the 
permanent ova, others break down and are used as the pabulum 
at the expense of which the protoplasm of the young ovum 
grows.” 
Judging from the number of cells in a fully formed cyst, 
there are at most four or five generations of secondary oogonia 
in the ovary of Bufo. After the last odgonial division resting 
nuclei are formed, and the cyst is filled with small cells which 
appear much like that shown in Fig. 20. At this time cell 
and nuclear boundaries are very much more indistinct than 
in earlier stages, yet they can readily be made out in prep- 
arations fixed in Flemming’s solution and stained with iron 
hematoxylin. If the material is properly preserved the cells 
never form a syncytium; nor is there any fusion of the nuclei, 
or any absorption by one nucleus of its less fortunate neigh- 
bors. Each cell in a cyst develops into an oocyte, and, al- 
though I have examined a large number of cysts in this stage 
of development taken from many different individuals, I have 
yet to find a single instance in which there is a degeneration 
of any of the germ-cells in a cyst or any change of germ-cells 
into follicle cells. It seems very probable that the cells which 
several investigators have considered to be degenerating young 
oocytes, were, in reality, cells in which the nuclei were in 
the condition shown in Fig. 25. This contracted state of the 
nuclear contents, to which McClung (62) has applied the 
term synizesis, is a definite constructive stage in the develop- 
ment of the young oocyte of Bufo, and it is not due in any 
way to a degeneration of the nucleus or of the cell. 
Owing to the crowded condition of the cells in a cyst the 
young o6cyte is more or less polygonal in outline. The nucleus 
is very large in proportion to the size of the cell, and it is 
invariably oval or slightly irregular, never possessing the 
polymorphic form characteristic of the nuclei in the earlier 
generations of cells. At this period the chromatin shows little 
capacity for staining and, as in the resting odgonia, it is in 
the form of minute granules which are either scattered along 
