Vol. XXVII. December, 1914. No. 6 



BIOLOGICAL BULLETIN 



SPERMATOGENESIS OF THE HORSE WITH SPECIAL 

 REFERENCE TO THE ACCESSORY CHROMO- 

 SOME AND THE CHROMATOID BODY. 



J. E. WODSEDALEK, 

 ZOOLOGY DEPARTMENT, UNIVERSITY OF IDAHO. 



CONTENTS. 



I. Introduction 295 



II. Material and Methods 296 



III. General Arrangement of the Germ Cells 297 



IV. Spermatogonia 297 



V. Primary Spermatocytes 298 



1. Resting Stage 298 



2. Synizesis and Growth Period 299 



3. Reduction Division 300 



VI. Secondary Spermatocyte 301 



VII. Spermatids 302 



VIII. Development of the Spermatozoa 302 



IX. Variation in Size of Adult Spermatozoa 305 



X. Migration of the Developing Spermatozoa 306 



XI. The Chromatoid Body 307 



XII. Summary 311 



I. INTRODUCTION. 



Many interesting things were observed in this study on the 

 spermatogenesis of the horse, but the two points of especial 

 interest and importance are; firstly, the occurrence of a large 

 accessory chromosome, and secondly, the presence of a much 

 smaller though very conspicuous body comparable to the chro- 

 matoid body as described by Professor E. B. Wilson ('13) in 

 Pentatoma. While the significance of the chromatoid body is prob- 

 lematical, it is a body of extreme interest in this connection on 

 account of its deceptive resemblance to an accessory chromo- 

 some. Were it not for the fact that its entire history can be 



295 



