THE EAKLY DEVELOPMENT OF THE PIGEON'S EGG, 



WITH ESPECIAL KEFERENCE TO POLYSPERMY 



AND THE ORIGIN OF THE PERIBLAST NUCLEL^ 



BY 

 MARY BLOUNT 



With 54 Figures. 



CONTENTS. 



PAGE. 



Introduction 2 



Value of the Material 2 



Amount of Material 2 



Acknowledgments 3 



I. Methods 3 



II, Distribution of nuclei during the lirst fourteen hours after fertiliza- 



tioin. Illustrated by charts 4 



III. Polyspermy 19 



(a) Polyspermy in Bryozoa, and Bonnevie's explanation of Poly- 



spermy 19 



(b) Polyspermy in Holothuroidea 21 



(c) Polyspermy in Insects 21 



(d) Polyspermy in Selachians 21 



Eiickert's explanation for the migration of the supernumerary 



sperms 22 



(e) Polyspermy in the Newt 23 



(f ) Polyspermy in Reptiles 23 



(g) Polyspermy in Birds 23 



(h) Tlie cause of the migration of the supernumerary sperm nuclei 



in the pigeon 24 



(i) Polyspermy in Plants, — Ephedra 26 



(j) Accessory cleavage and segn)entatiou of egg fragments 27 



(Iv) "luwandering Follicular Cells" 27 



(1) Evidence of the disappearance of the supernumerary nuclei in the 



pigeon and comparison with other meroblastic vertebrate eggs 30 



(m) Function of the supernumerary sperms 33 



IV. Area of Primary Cleavage 35 



(a) Maturation Stage 35 



(b) Direction of the First Cleavage Plane 35 



(c) The 4-celled stage 37 



Asymmetry 37 



(d) The 8-celled and later stages 41 



V. The Segmentation Cavity 46 



Description by Duval 46 



Description by Kolliker 47 



^A dissertation submitted to the faculty of the Ogden Graduate School of 

 Science, University of Chicago, in candidacy for the degree of Doctor of Phi- 

 losophy. 

 The Jouexal of MoRrHOLOGY — Vol. XX, No. 1. 



