GERM CELLS OF ANURANS 263 
rare cases these abnormal spermatid-like bodies apparently give 
rise by condensation of the nuclear material and elongation of 
the cytoplasm to structures bearing a faint resemblance to the 
apyrene spermatozoa of certain prosobranchs. 
The degeneration of the first-season spermatocytes at the meta- 
phase is somewhat analogous to the degeneration of that type of 
ova that requires the stimulation of a spermatozoon to enable it 
to complete the developmental cycle. Mead ('98) and Conklin 
('05) both observed ova with perfectly formed spindle and chro- 
mosomes go to pieces at this stage without further development 
unless fertilized. In the case of the larval bullfrog spermato- 
cytes, fragmentation of the centrosome is the immediate cause of 
the failure of the cells to divide and of the resulting degeneration. 
Professor Conklin has suggested that perhaps the non-fertilized 
ova observed by him also go to pieces because of centrosomal 
fragmentation. It is known that the entering spermatozoan 
brings in a centrosome which takes part in the cleavage process. 
In regard to the abortive maturation cycle of the first-year bull- 
frog larvae it is possible that it is a vestige of an early repro- 
ductive cycle inherited from remote ancestors. Centrosomal 
fragmentation is merely the more obvious morphological cause 
of the degeneration of the spermatocytes and itself a symptom 
of a deeper-seated derangement of cellular life. 
Cytoplasmic and nuclear changes in the degenerating spermatocytes 
of first-year larvae 
The nuclear changes are more or les characteristic of degenerat- 
ing cells in general, including those just described as ultimately 
destined to form the spermatid-like bodies. The initial stage in 
degeneration apparently first affects the centrosome, the chromo- 
somes and cytoplasm are later attacked. To take a typical 
example of degeneration in a spermatocyte (omitting those poly- 
asters where the chromosomes are pulled to pieces), there is first 
fragmentation of the centrosome and formation of polyasters, 
followed by shortening and thickening of the tetrads accom- 
panied by increased staining capacity. The chromosomes soon 
lose the ring-tetrad structure, and the annular space entirely dis- 
