STUDIES ON THE CELLS OF CATTLE WITH SPECIAL 



REFERENCE TO SPERMATOGENESIS, OOGONIA, 



AND SEX-DETERMINATION. 



J. E. WODSEDALEK, 

 ZOOLOGY DEPARTMENT, UNIVERSITY OF IDAHO. l 



CONTENTS. 



I. Introduction 290 



II. Material and Methods 293 



III. General Arrangement of the Male Germinal Cells 294 



IV. Spermatogenesis 294 



1. Spermatogonia 295 



2. Primary Spermatocytes 296 



3. Secondary Spermatocytes 297 



4. Spermatids 297 



V. Dimorphism in the Spermatozoa 297 



VI. Oogonia 298 



VII. Chromosomes in Somatic Cells 300 



VIII. Sex- Chromosomes in Relation to Sex-Determination 302 



IX. Sex Ratio in Cattle 303 



X. Sex-Limited Inheritance in Cattle 304 



XI. The Free-Martin 305 



XII. Summary 305 



I. INTRODUCTION. 



Sex-determination with its many attendant problems has 

 always been a subject of great interest to practical animal 

 breeders; and the art of breeding has always been replete with 

 rules by which the sex ratio might be shifted in various ways 

 to the advantage of the breeder. These rules, however, have 

 been founded upon inadequate evidence and unsound reasoning. 



The most common beliefs in regard to sex control have from 

 time to time been founded on heat relations, some maintaining 

 that the products of conception in early heat were more often 

 males, others that they were more often females. Pearl and 

 Parshley ('13) have published data on sex-determination in 

 cattle with the following conclusions: (i) That as the time of 

 coitus approaches the end of the cestrous period there is a pro- 



1 This research was supported in part by the Adams Fund of the Idaho Experi- 

 ment Station. 



290 



