16 THE hen's egg. [chap. 



with an abdominal opening. 2nd. A long tubular 

 portion — the oviduct proper — opening by a narrow neck 

 or isthmus into the 3rd portion, which is much dilated, 

 and has been called the uter us ; the 4th part is some- 

 what narrow, and leads from the uterus into the cloaca. 

 The whole of the mucous membrane lining the oviduct 

 is largely ciliated. 



The accessory parts of the egg are entirely formed 

 in the 2nd and 3rd portions. The layer of albumen 

 which immediately surrounds the yolk is first de- 

 posited ; the clialaz^_ are next formed. Their spiral 

 character and the less distinctly marked spiral arrange- 

 ment of the whole albumen is brought about by the 

 motion of the egg along the spiral ridges into which 

 the interior of the second or tubular portion of the 

 oviduct is thrown. The spirals of the two chalazae are 

 in different directions. This is probably produced by 

 their peripheral ends remaining fixed while the yolk to 

 which their central ends are attached is caused to 

 rotate by the contractions of the oviduct. During the 

 formation of the chalazse the rest of the albumen is 

 also deposited ; and finally the shell-membrane is formed 

 in the narrow neck of the 2nd portion, by the fibrilla- 

 tion of the most external layer of albumen. The eo-g 

 passes through the 2nd portion in little more than 

 3 hours. In the 3rd portion the shell is formed. The 

 mucous membrane of this part is raised into nume- 

 rous flattened folds, like large villi, containing follicu- 

 lar glands. From these a thick white fluid is poured 

 out, which soon forms a kind of covering to the egg, in 

 which the inorganic particles are deposited. In this 

 portion of the oviduct the egg remains from 12 to 18 



