ANA TOMY OF BIRDS 



225 



bones so named, and others of the upper jaw. This subocular bar 

 is an antero-superior part of the first post-oral arch, of which 2 and 

 mk are a postero-inferior portion ; the cleft of the future mouth is 

 to lie between them. The lower jaw-bone, or mandible, is entirely 

 developed from mk, its several bones developing around this rod of 

 cartilage, which is called the Meckelian cartilage ; it is to become 



e./; i. 



-'^A t'^'J'-^" 



Fig. 64.— Skull of chick, fifth clay of incu- 

 bation, X 9 diameters. Seen from above, 

 the membranous roof of the skull and the 

 brain removed, cul, anterior cerebral vesicle ; 

 e, eye ; c, notochord, running through the 

 middle of the basilar plate or parachordal 

 cartilage, in which are already visible the 

 rudimentary ear-parts, cl, the cochlea, )isc, 

 the horizontal semicircular canal ; jrfs, the 

 pituitary space, bounded by ti\ the trabe- 

 culse, which come together before it to form 

 the frontonasal plate, fa in Fig. 65 ; Ig, lin- 

 gula or bridge, connecting trabecule with 

 parachordal cartilage ; 5, notch afterwards 

 becoming foramen ovale for passage of parts 

 of the fifth (trifacial) nerve ; 9, foramen for 

 hypoglossal nerve ; q, separate cartilage 

 forming the future quadrate bone. (After 

 Parker, in Ency. Brit.) 



c.%. C.&J'. libii L,^. 



Fig. 65. — Same as Fig. 64, but seen from below. 

 Cfl, anterior cerebral vesicle ; e, eye ; m, mouth ; 

 %iis, pituitary space ; fn, frontonasal plate ; tr, 

 ends of the trabeculie, free again after their union 

 and bent strongly from the original axis of the 

 trabeculse ; ii, external nostril ; mxp, subocular 

 bar of cartilage, or pterygopalatine rod, to form 

 ■pa, palatine, and fg, pterygoid bone, and other 

 parts of the upper jaw, as the maxillary, jugal, 

 and quadratojugal ; q, quadrate cartilage, sanie 

 as seen in Fig. 64 ; vik, Meckelian cartilage, to 

 form lower jaw — these parts are in the first 

 postoral visceral arch ; ch, ceratohyal, and Wt, 

 Isasihyal, of second postoral arch ; vhr, cerato- 

 branchial, ehr, epibrancliial, &&/', basibranchial, 

 of third postoral arch ; the parts of the second 

 and third arch all going into the hyoid bone. 1, 

 2, 3, 1st, 2d, 3d visceral clefts, whereof the 1st is 

 to be modified into the ear-passages and the 

 others are to be obliterated. (After Parker.) 



movably articulated with the bone, the quadrate, into which q will 

 be transformed. Thus the postero-inferior part of the first postoral 

 arch (second of the whole series of arches) begins in two pieces, one 

 of which is to become the susjMmsorium, or suspender of the mandible, 

 and the other the mandil)le itself. The rest of the pieces belong to 

 the second and third postoral arches, and all together make up the 

 very composite h>/oid bone, or bone of the tongue (Figs. 72, 73, 74). 

 The pieces di and bh are in the second arch, and form respectively 



Q 



