POSTERIOR 



SEMICIRCULAR 



CANAL 



Jeve n? .h^ ^ /"■ J'"'''u'''u '''''°" '^^'^"^'^ developing rhombencephalon at the 

 lZ\ . f P'^'""^'" ^hich are beginning to sink inward below the surrounding 



ectoderm epidermis). (B) The otic vesicles are forming in this 19 somite (about 

 thhT ;"^"^^^'°")'^h.ck embryo. Slight constriction of otic vesicle near .,s junction 

 with the ectoderm. (C) Left otic vesicle of 4.3 mm. human embryo. The small 



850 



