. A manual of zoology. Zoology. 516 CHORDATA ratus appears. The spiracular deft persists as a canal, opening into the pharynx by the Eustacliian tuhe, its outer end expanded into the tym- panum, closed externally by the tympanic membrane, supported by the tympanic annulus (tlotted circle in tig. 566). The connexion of the labvrintli with tlie tympanum is an opening in the otic capsule, the fenestra ovalis, in which is the stapes (? part of capsule), the columella extending from this to the tympanic membrane â \li\l/f And carrying the sound waves across to the fif/i^ inner ear. The brain (
. A manual of zoology. Zoology. 516 CHORDATA ratus appears. The spiracular deft persists as a canal, opening into the pharynx by the Eustacliian tuhe, its outer end expanded into the tym- panum, closed externally by the tympanic membrane, supported by the tympanic annulus (tlotted circle in tig. 566). The connexion of the labvrintli with tlie tympanum is an opening in the otic capsule, the fenestra ovalis, in which is the stapes (? part of capsule), the columella extending from this to the tympanic membrane â \li\l/f And carrying the sound waves across to the fif/i^ inner ear. The brain (fig. 56S) has advanced --^ above that of the fishes in the stronger develop- Xol nrent of the cerelirum, but remains l)ehind in the small size of the cerebellum, which is but â¢^ a thin lamella. The respiratory organs afford important ^^" F' Ife * characters, since both gills and lungs occur. The larvK of the anura, as a rule, have inter- Zâ J^^O^^^ ^'^^^ g'lls, but the dorsal part of these, as in ZlS' / â ^'^ %k many fishes, develop early and very strongly ilffi -XxS: A, ;7 aiid extend out through the clefts to the skin â , ^,^ ^_ , above them as three pairs of external eills. jsM [--^SteiMj^' i ^ These, however, are absorbed with the develop- -^Tff -*^'^H / ment of the other gill lea^â es, which become ji<^ l"-^» I enclosed in a special chamber {atrium) by the backward growth of an opercular fold from each hyoid arch. The atrium usually opens Fig. of frog, to the exterior by a spiracle on the ijft side, 7, line between olfactory lobes ' and cerebrum; Frh, fossa but occasionally there are a pair of spiracles. rhomboidaUs, HH^ cerebel- -phe external gills are strongly developed in mm; /, ollactory nerve; Lol, ^ '- - ^ olfactory lobes; MH^ optic the larval urodeles and cxciliaus, and the in- SSs!1^:'lwixt b;^n:^'''- f^'^^'l gi"« -'^ correspondingly undeveloped. The paired lungs open into the hinder part of the pharynx, either directly
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
