Vol. XIII. October, igoy. No. 5. 



BIOLOGICAL BULLETIN 



THE EARLY DEVELOPMENT OF THE PIGEON'S 



EGG, WITH ESPECIAL REFERENCE TO THE 



SUPERNUMERARY SPERM NUCLEI, 



THE PERIBLAST AND THE 



GERM WALL. 



MARY BLOUNT. 



A Preliminary Paper. 



In the American Journal of Anatomy, September, 1 904, there 

 appeared a paper by Dr. E. H. Harper on " The Fertilization and 

 Early Development of the Pigeon's Egg." Dr. Harper found 

 that the egg is polyspermic ; that one sperm nucleus unites with 

 the egg nucleus ; and that the supernumerary sperm nuclei mi- 

 grate to the periphery of the germinal area and there set up 

 an accessory cleavage. He followed through the development 

 to the sixteen-cell stage, or about eight hours after fertilization, 

 and although he gives two figures of sections of an egg fifteen 

 hours after fertilization, the intervening stages were not filled in. 



At the zoological laboratory of the University of Chicago, in 

 January, 1905, I took up the study of the pigeon's egg, hoping 

 to continue from the sixteen-cell stage. But in order to appre- 

 ciate the material, it was necessary to go back into earlier stages. 

 I have obtained an egg for every hour of development from the 

 formation of polar bodies to the time of laying — a period of about 

 forty-one hours. For some of the more critical stages before 

 laying I have more abundant material, and also have a good 

 many laid eggs. 



The purpose of this preliminary paper is to announce some of 

 the more important steps in the early development, but without 



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