RL 



B 



CH BR.+ BR.3BR.2BR.I 



FIG. 32. A. THE SKULL OF A I2-MM. TADPOLE, SEEN FROM 



THE RIGHT SIDE. THE NOTOCHORD, THE BRAIN, AND THE ENTIRE 

 HEAD ARE REPRESENTED IN OUTLINE, IN ORDER TO SHOW THE RE- 

 LATIONS OF THE SKULL TO THEM. 



B. THE SAME SKULL FROM THE DORSAL SURFACE. THE LOWER 

 JAW AND THE HYOIDEAN AND BRANCHIAL BARS ARE OMITTED. 



C. SAME SKULL FROM THE VENTRAL SURFACE. (A, B, and C 

 are all from Marshall.) 



B B, basi-branchial. BH, roof of hind-brain. B M , roof of mid-brain. 

 BRA, B R.2, B R3, B RA, first, second, third, and fourth branchial bars. BS, 

 cerebral hemisphere. C//, notochord. EC, auditory capsule. H B, basihyal. 

 HO, urohyal. H Q, articulation of ceratohyal with quadrate. H R, ceratohyal. 

 jfL, lower jaw. fU* upper jaw. L I, upper lip. L J, lower lip. LL, lower 

 labial cartilage. L /, upper labial cartilage. M C, Merkel's cartilage. PN, 

 pineal body. Q, quadrate. Q O, orbital process of quadrate. QP- palato-ptery- 

 goid process. Q /?, connection of quadrate with trabecula. R C, paracordal 

 cartilage. R L, trabecula cranii. SA, membranous patch in which stapes is de- 

 veloped later. X, choroid plexus of third ventricle. 



86 



