GERM CELLS OF ANURANS 295 
centrosomal behavior is but a symptom of a deep-seated proto- 
plasmic disorganization of the larval sex cells. 
16. Giant spermatid-like structures are formed by the suppres- 
sion of the first and second maturation divisions and the growth 
of an axial fiber from the centrosome. These bizarre structures 
degenerate. 
17. The cells of the first larval sexual cycle degenerate and dis- 
appear gradually. A few cells, lineal descendants of the primor- 
dial germ cells, persist unchanged through the cycle of matura- 
tion and degeneration, and give rise by repeated mitosis to a 
second germ-cell generation in larvae just about ready for meta- 
morphosis. This second cell generation is small in size. 
18. Shortly before metamorphosis, this second generation of 
germ cells undergoes a second sexual cycle, characterized by the 
formation of normal spermatozoa. The cells and chromosomes 
are comparable in every way with those of the adult frog and 
are smaller than the larval cells and chromosomes. 
19. The second larval sexual cycle is normal in every respect. 
There is no degeneration of the sexual elements. The matura- 
tion cycle is normal, as are also the spermatozoa, despite the fact 
the animal is a larva with the efferent ducts of the testis incom- 
pletely formed. 
20. In so far as the possession of ripe spermatozoa is concerned, 
the larval bullfrog at metamorphosis may be said to be mature, 
and in this respect resembles the axolotl. 
21. The germ cells of female larvae at the time of metamor- 
phosis are not mature, but are young occytes undergoing growth. 
The writer has some evidence that, like the male, the female 
larvae may also show a precocious and abortive maturation cycle. 
This point is now under investigation. 
22. The question of hermaphroditism and the sex ratios of the 
Anura is not dealt with in this paper, but forms the subject-matter 
of a later communication. 
THE JOURNAL OF EXPERIMENTAL. ZOOLOGY, VOL. 32, NO. 2 
