AUTHOK S ABSTRACT OF THIS PAPER ISSDEI) 
BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 6 
THE GERM CELLS OF ANURANS 
I. THE MALE SEXUAL CYCLE OF RANA CATESBEIANA LARVAE 
WILBUR WILLIS SWINGLE 
Department of Biology, Princeton University 
TWO TEXT FIGURES AND FIFTEEN PLATES (ONE HUNDRED AND THIRTY-ONE FIGURES) 
CONTENTS 
Introduction 236 
Division of the problem 237 
Material and methods 238 
Resume of a few of the more important points in the developmental history 
of the germ glands and germ cells of Rana catesbeiana larvae 241 
Observations. Sexual cycle first-year larvae. Primary and secondary 
spermatogonia 246 
Last spermatogonial division. First-year tadpoles 249 
Diakinesis : Formation of the tetrads 256 
The heterotypic mitosis of first-year larval spermatocytes 260 
Fragmentation of the centrosome of first-year larval spermatocytes .... 261 
Cytoplasmic and nuclear changes in the degenerating spermatocytes of 
first-year larvae 263 
Maturation cycle of second-year larvae and formation of functional 
spermatozoa 265 
Discussion of observations -68 
1. Amitosis 268 
2. The polymorphic nuclei of amphibians 269 
3. Synapsis 272 
4. The chromoplasts : (?) Karyosomes 275 
5. Significance of the maturation cycle in the larvae 276 
6. Is there a precocious sexual cycle in other anurans? 277 
7. Significance of degeneration of sexual elements derived from primor- 
dial germ cells 279 
Summary of Conclusions 291 
A. The origin and fate of the primordial germ cells 291 
B. The chromosomes and larval sexual cycles 293 
Literature Cited 296 
235 
