. The development of the chick; an introduction to embryology . iuph. and other luesenchymalparts of the intcMiial (>ar. and (2) to foi-m the auditory ossicles ofthe middle eai. Thus th(> (>ar furnishes a strikinu example of thecombination of oriiiinally diverse components in the formationof a siuiile oruan. Jdie coui-se of evolution of this com]:)lex sense-organ is thus illustrated in the embryonic development; in theSelachia the hyoinaiulibulai chft is a comnumication betweenpharynx and exterior, like the branchial Ilcfts, and still preservesto a ceitain (>\tent th(> respirato
. The development of the chick; an introduction to embryology . iuph. and other luesenchymalparts of the intcMiial (>ar. and (2) to foi-m the auditory ossicles ofthe middle eai. Thus th(> (>ar furnishes a strikinu example of thecombination of oriiiinally diverse components in the formationof a siuiile oruan. Jdie coui-se of evolution of this com]:)lex sense-organ is thus illustrated in the embryonic development; in theSelachia the hyoinaiulibulai chft is a comnumication betweenpharynx and exterior, like the branchial Ilcfts, and still preservesto a ceitain (>\tent th(> respiratory fmictio!i. The eml)rvonichistory furnishes a summai\ (.f the wa\ in wliich it was uraduallv ORGANS OF SPECIAL SENSE 289. drawn into the service of the otocyst in the course of evolu-tion. Development of the Otocyst and Associated Parts. In tlie pre-ceding chapter we look ii]) the fonriation of the otocyst and theorigin of the endolymphatic duct. The latter is at first an apicaloutgrowth from the otocyst, but its attachment soon becomesshifted to the median side of the otocyst, owing to the expansionof the dorsal external wall of thelatter (Fig. 167). Three divisionsof the otocyst may now be (hstin-guished: (a) ductus endolymphaticusor recessus labyrinthi; (b) pars su-]jeii()r l;il)yriiithi; (r) pais inferi(n-labyiintlii. The boundary l)etweenthe two latter is rather indistinctlyindicated at this stage by a shallowgroove on the median face of theotocyst. The development of theseparts may now ])e followed separately. (a) The Development of the DuctusEndolymphaticus. It was noted in(ha|)ter VI that the ductus endolym-phaticus is united to the epidermisby a stiand of cells that preserves alumen up to the st
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