CHAPTER II 

 THE DEVELOPMENT PRIOR TO LAYING 



I. Maturation 



During the growth period the germinal vesicle has increased 

 to an enormous size (455 x 72 ju in an ovmn 37 mm. in diameter, 

 Fig. 8). It lies in contact with the vitelline membrane. The 

 margins of the lenticular nucleus are folded into the interior in 

 such a way that sections give an effect of rod-shaped bodies spring- 

 ing from the membrane which were doubtfully interpreted as 



^'-^ 



Fig. 8. — Vertical section of germinal vesicle of hen's egg after Sonnenbrodt. 

 Size of egg 37 mm. in diameter; size of nucleus 455Mx72/i. 



chromosomes by Holl. The real chromosomes are however in 

 the center in the form of double rods (Fig. 8). The maturation 

 divisions of the hen's egg have not been described, but we have 

 fortunately a very good account of the maturation and fertiliza- 

 tion of the pigeon's egg by E. H. Harper, which furnishes the 

 basis of the following description: 



The wall of the germinal vesicle begins to break down in 

 ovarian eggs of about 18.75 mm. diameter, the full size of the egg 

 of the pigeon being about 25 mm. Part of the fluid contents of 

 the germinal vesicle flows out and forms a layer outside the disinte- 



32 



