392 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



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

 concave surface being Uned by a thick layer of columnar 

 epiblast. The recessus labyrinthi 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- 



PiG. 130. 



Section of the Head of a F<etal Sheep 20 mm. in 

 LENGTH. (After Bottcher.) 



R. V. recessus labyrinthi ; V.B. vertical semicircular canal ; HB. 

 liorizontal semicircular canal ; G.C. cochlear canal ; O. coch- 

 lear ganglion. 



