THE BILATERALITY OF THE PIGEON'S EGG 



A. STUDY IN EGG ORGANIZATION* FROM THE FIRST GROWTH PERIOD 

 OF THE OOCYTE TO THE BEGINNING OF CLEAVAGE 



Part I 



GEORGE W. BARTELMEZ 



From the Department of Zoology, The University of Chicago 



FORTY-SEVEN FIGURES 



CONTENTS 



I. Introduction 270 



II. Material and methods 271 



III. The problem 275 



IV. The ovarian history 277 



A. The primordial follicle. Oocytes less than 90m 277 



B. The second growth period. Oocytes to 0.4 mm 281 



1 . The lipoid spherules and the yolk nucleus 282 



2. The origin of the stigma and the follicular blood supply 283 



C. The period of differentiation. Oocytes to 5.0 rqm 286 



1. The eccentricity of the germinal vesicle 286 



2. The ooplasmic zones 287 



3. The peripheral migration of the germinal vesicle ; 287 



4. The zona radiata and the rotation of the oocyte 288 



D. The final growth period. Oocytes to 20 mm 290 



1. The initial stimuli 290 



2. Correlations in the reproductive apparatus 291 



3. The orientation of the follicle and ovulation 292 



V. The bilaterality of the blastodisc. (A summary of Part II) 296 



A. The origin and development of the blastodisc 296 



B. The blastodisc during maturation and first cleavage 298 



VI. Axis angles 299 



The long, chalazal and embryonic axes 300 



VII. Discussion and summary 304 



A. Bilaterality in vertebrate ova 304 



B. Summary of results 307 



C. Conclusions 309 



Bibliography 310 



269 



