THE OVIDUCTS 



221 



portions, tlie walls are thinner and the glands are absent, and the 

 himen is lined with colnmnar cells. Kgfjs may collect in the dilated 

 portion until a female is clasped hy a male, when the e<jgs are 

 liberated and fertilized externall\- in the water. The secretion of 

 the oviducts absorbs considerable water, and a characteristic mass 

 of gelatinous material surrounds the eggs shortly after fertilization. 

 Reptiles and Birds. In the case of reptiles and birds, the albumen 

 surrounding the ()\um is produced from glands in the wall of the 

 anterior part of the oviduct, and the shell which surrounds it is 

 formed by glands in the posterior region. Naturally, in cases of 

 animals with shelled eggs fertilization takes })lace in the oviduct 

 anterior to the shell glands. 



Ciliated col 

 epHhclium^ 



Glands d^^ r 



Connective 

 tissne 



Circular STVooth muscle 



Longitudinal smooth inuscle 



Fig. 138. — Drawing of a section through the oviduot of a turtle. 



The wall of the o\'iducts here is generally composed of the follow- 

 ing coats. The mucosa has a lining of ciliated columnar cells and 

 tubular glands that become active and large in breeding seasons. 

 The submucosa of fibroelastic connecti\'e tissue forms folds that 

 carry the mucosa into the lumen. The muscularis has a broad 

 circular and a narrower longitudinal layer of smooth muscle. An 

 adventitia, or superficial coat, varies from a minute amount of 

 connective tissue covered by the mesentery to a relatively broad 

 region in some forms. (Fig. 138.) 



Mammals.^ In monotremes there is still but one external passage- 

 way for both the urogenital and digestive systems, the cloaca. In 



