152 



GENERAL ORNITHOLOGY. 



nasal plate, wliich is so arched over do\ATiward as to disappear from this view, as seen in 

 fig. 65, where fn is The tVouto-uasal process, and u is the future external m.istril. After 

 uniting in the inter-nasal phite, the fore ends uf the trahccuhv separate and become free ; their 

 free ends are the under extremities of this Jirst cisceral arch (first and only pre-oral arcli). 



The same chick's head, now viewed from heluw, fig. 05, shows the squarish aperture, m. 

 of the future mouth; the three post-oral arches, with their respective cartilaginous hars, out 

 of wliich are to he formed the hones of the jaws and tongue. 1, 5. 3. are the coiTespondiug 

 visceral clefts, between the arches ; the first of these is to he modelled into the car- 

 passages (outer and middle ear and eustachian tube) : the others will disappear. The qundrnte 

 cartilage, q, is the same that was seen in fig. 04 ; it is already nearly in position, between the 

 hind ends of the scaffolding of the npper and under jaw. The curved suhocuJar or maxiUo- 

 palati)i€ bar, ma:p, developed in the first post-oral arch, already indicates ixiiteviorly jjaJatine, 

 pa, and posteriorly, pterygoid, pg, parts : it will fonn the bones so named, and others of the 



Fig. &4. — Skull of cliiok, tifcti ilay nf incubation. 

 X9 diameters. Seen from above, the uienibrannus roof 

 of the skull and the brain removeil. oil, anterior cere- 

 bral vesicle : e, eye : r, notoohord, running through the 

 middle of the basilar plate or parachordal cartilage, in 

 which are already visible the rudimentary ear-parts, cl . 

 the cochlea, hsc, the horizontal semicircular canal : ;>r>t, 

 the pituitary space, bounded by tr, the trabeculre, 

 which come together before it to form the fronto-nasal 

 plate, fii. in lig. (>o: Jr). /i»;/>ila or briilge connecting 

 trabecula" with pnracbordal cartihige : 'i, notch after- 

 ward becoming foramen ovale for passage of parts of 

 the fifth ^trifacial^ nerve ; 0. foramen for hypoglossal 

 nerve: q, separate cartilage forming the future quad- 

 rate bone. {After Parker, in Encp. Brit.) 



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

 crl, anterior cerebral vesicle; c, eye; m, mouth ; /^^■J, 

 pituitary space; /'/i, fronto-nasal plate; (r, ends of the 

 trabeculse, free again after their union and bent strong- 

 ly from the original axis of the trabecuhe; », exter- 

 nal nostril ; mxp, subocular bar of cartilage, or ptery- 

 go-palatine rod, to form pa, palatine, and />(;. pterygoid 

 bone, and other parts of the upper jaw, as the maxil- 

 lary, jugal and quadrato-jugal; (/. quadrate cartilage, 

 same as seen in lig G-1; mk, meckclian cartilage, to form 

 lower jaw; these parts are in the lirst post -oral visceral 

 arch; eft, cerato-hyal, and bh, basihyal. of second post- 

 oral arch : chr, cerato-branchial. thr, cpi-branchial, 

 ?)frr. basi-brauchial, of third post-oral arch; the larts 

 of the second and third nrch all going into the yoid 

 bone. 1. 2. 3. 1st. -Jd, 3d visceral clefts, whereof lue 1st 

 is to be moditicd into the ear-pass;iges. and the others 

 are to be obliterated. (After Parker.) 



upper jaw. This snborular bar is an antero-snperior part of the first post-oral arch, of which 

 7 and ml- are a postero-inferior portion ; the cleft of the future mouth is to lie between them. 

 Tho lower jaw bone, or mandihle, is entirely developed from m'k, its several bones developing 

 around this rod t)f rartihiee, the wecl'eUau cartilage : it is to bectune movahly articulated with 

 the bone, the quadrate, into which q \nll be transformed. Tlins the pi^stero-inferior part of 

 the first post-oral arch (second of the whole series of arclies) begins in two pieces, one of which 

 is to become the .susjyensorinm, or suspender of the mandible, and the other the mandible 



