GERM CELLS OF ANURANS 249 
fixed material. The chromatin masses are readily counted and 
are of the diploid number. This type of cell is unusual in the 
larvae, and has never been observed in metamorphosed frogs. 
In metaphase the apices of the J-chromosomes are oriented 
toward the center of the spindle, and spindle fiber attachment is 
non-terminal. 
The spermatpgonial chromosomes are occasionally split into 
two elements twisted about each other as apparently is the usual 
condition in Ambystoma (Parmenter, '20). 
Variations in the chromosome number have been observed in 
but two cases : once in a spermatocyte which contained eighteen 
tetrads, possibly the result of fusion of two adjacent cells, and once 
in a spermatogonium containing thirty-six or more chromosomes 
(fig. 19). 
It is doubtful if variation of chromosomal number occurs in 
normal cells within one and the same individual, save perhaps in 
those cases where a single chromosome may occasionally undergo 
fragmentation. Even in such cases there is apparently no real 
variation in quantity of chromatin mass. Such chromosomal 
fragmentation as is described by recent writers, notably Hance 
('18), has not been observed in the bullfrog except in degenerating 
first spermatocytes where the multipolar spindles literally tear 
the chromosomes to pieces (fig. 115). 
The multiphcation of secondary spermatogonia in the larval 
gonad, and this is especially true of first-year tadpoles, does not 
continue long enough to obliterate the lumen of the gland or to 
crowd the cells together owing to greatly increased numbers. 
During the second season the spermatogonial divisions come to 
a close and maturation begins in the type of gonad shown in 
figures 33 and 34, also text figure 1, A. 
Last spermatogonial division. First-year tadpoles 
The telophases of the last larval spermatogonial divisions 
differ in no respect from other similar stages in the mitosis of the 
primary and secondary spermatogonia. The period of nuclear 
reconstruction, however, presents marked structural changes dif- 
ferentiating it from all previous stages, in that the nucleus enters 
