THE SKULL. 



329' 



In front of tlienotocliorcl, the paradiorclals are continued for- 

 wards as a pah' of short and rather slender rods, the trabeculsB 

 cranii : these lie at the sides of the pituitary, body, and unite in 

 front of this to form the ethmoidal plate, which underlies and 

 supports the fore-brain. 



By the eighth day (Figs. 131 and 116) important changes 



SF PC OM SE 



AR Qj 



B"iG. 131. — The skull of a Chick Embrjo at the end of the eighth day of incu- 

 bation ; seen from the right side. The head and eye are represented in 

 outline, x 10. 



AN", angulare. AR, articular portion of manrlibiUar bar. BB, basi-branchial 

 cartilage. BK, cerato-branclual cartilage. CL, coluiuella. EH, external or hori- 

 zontal semicircnlar canal. EP, posterior vertical semicircnlar canal. ET, mesethmoid 

 cartilage. FE, fenestra ovalis. HR, ceratoliyal cartilage. MC, Meckers cartilage. 

 OC, occipital condyle. OK, slit-like apertm-c of olfactory capsule. OL, outline of 

 lens. OW, outline of eyeball. PG, pterygoid. Q,, quadrate cartilage. Q J, quadi-ato- 

 jugal. RL, trabecula cranii. SE, pre-sphenoidal region. SE, ali-spbenoidal region. 

 SL, supra-occipital region. SR supra-angidar. 



have occurred in the skull, mainly associated with the growth 

 forwards of the beak. 



At the hinder end of the skull the two parachordal cartilages 

 (Fig. 116, EC) have united, above and below the notochord, to form 

 the basilar plate ; and the sides of the basilar plate, including the 

 auditory capsules which are fused with them, have grown up- 



