392 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



canal (GG) becomes longer and curved; its inner and 

 concave surface being lined by a thick layer of columnar 

 epiblast. The recessus labyrinth! also increases in 

 length, and just below the point where the bulgings to 

 form the vertical semicircular canals are situated, there 

 is formed a fresh protuberance for the horizontal semi- 



Fio. 130. 



Section of 



THE Head op a F(btal Sheep 

 LENGTH. (After Bottoher.) 



20 MM. IN 



R. V. recessus labyrinth! ; V.B. vertical semicircular canal ; HB. 

 horizontal semicircular canal ; G.G. cochlear canal ; O. coch- 

 lear ganglion. 



