14 THE hen's egg. [chap. 



course of the maturation of the ovum concern the body 

 of the cell rather than the germinal vesicle. As the 

 body grows in size a number of granules make their 

 appearance in its interior. These granules are formed 

 by the inherent activity of the protoplasm, which is 

 itself nourished, in a large measure at any rate, by the 

 cells of the follicle. The outermost layer of the proto- 

 plasm remains free from these granules. As the ovum 

 grows older the granules become larger, first of all in 

 the centre, and subsequently at the periphery, and take 

 the form of white yolk-spherules. The greater part of 

 them become at a later stage converted into yellow 

 yolk-spheres, while a portion of them, situated in the 

 position of the white yolk of the ripe ovum, retain their 

 original characters. 



The germinal vesicle, which in the youngest ova is 

 situated centrally or subcentrally, travels in the course 

 of the growth of the ovum towards the periphery, and 

 the protoplasm immediately surrounding it remains 

 relatively free from yolk granules, and so constitutes 

 the germinal disc. In the younger ova there is but a 

 single germinal spot in the germinal vesicle, but as the 

 ova enlarge several accessory germinal spots make their 

 appearance, while in the ripe ovum it seems doubtful 

 whether there is any longer a trace of a germinal 

 spot. 



The cells of the follicular epitheUum are at first 

 arranged in a single row, but at a later stage become 

 two or more rows deep : they undergo however a 

 nearly complete atrophy in the ripe ovum. Around 

 the follicular epithelium there is present a membrana 

 propria, and in the later stages of the growth of the 



