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
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