NIDAMENTAL TISSUES 



489 



result of having the cell bodies with 

 their contained nuclei at so many lev- 

 els, would be to make it serve as a strati- 

 fied epithelium. 



The oviduct of the fowl acts very 

 much as that of the skate did. It 

 differs functionally from that of the 

 skate in producing more various and 

 more numerous coverings for the egg. 

 We shall compare its structure briefly 

 with that of the skate by describing the 

 epithelial lining of an upper and a lower 

 region. 



A section taken near the beginning 

 (Fig. 459) shows that here the tube is 

 lined with a columnar epithelium which 

 is simple, but whose nuclei are placed 

 at somewhat various heights in the 

 cells. This gives a result which may be 

 compared with the strange epithelium 

 found in the skate's lower oviduct. The 

 nuclei are found only distally in the 

 layer, which is exceptional. The cells 

 show no signs of secretion, which may 

 be accounted for by the fact that the 

 hen was not laying at the time she was 

 killed. A section taken in the lower 

 part of the tube shows a decided differ- 

 ence from the skate's corresponding tis- 

 sue (Fig. 460). This region, besides its 

 simple epithelium, is invaginated into 

 numerous glands whose ducts and 

 mouths are, for some unknown reason, 

 very difficult to see. This was also the 

 case in other nidamental glands, as the 

 salamander and the invertebrate forms, 

 and seems to be a characteristic of this 

 tissue. 



The glands are lined by a cuboidal 

 epithelium whose nuclei are round, and 

 whose lumen but rarely shows in our specimen. It would probably 

 show better in a laying hen. The nuclei of the superficial cells are long 

 and narrow; more so than in the same kind of cells from the first region. 



FIG. 458. Raja erinacea; oviduct. 

 Thick, stratified epithelium whose 

 cells are distally elongate. X 450. 



