. Biology of the Heteromyidae. Heteromyidae. 282 LAY Q A N O P V. Fig. 9.—The Organ of Corti in the third half turn of D. merriami. DC and three white arrows = Deiter's cells (three rows), HC = Henson's cells, IHC = inner hair cell, OHC = outer hair cells (three rows), PC = pillar cells (inner and outer), SL = spiral ligament, TC and CANOPY = tectal cells and tectal canopy, TM = tectorial membrane, ZP and arrows = zona pectinata of basilar membrane containing hyaline mass, ZT = zona tecta of basilar membrane. omys, Perognathus, and Chaetodipus are each similar and intermediate to the ex- treme
. Biology of the Heteromyidae. Heteromyidae. 282 LAY Q A N O P V. Fig. 9.—The Organ of Corti in the third half turn of D. merriami. DC and three white arrows = Deiter's cells (three rows), HC = Henson's cells, IHC = inner hair cell, OHC = outer hair cells (three rows), PC = pillar cells (inner and outer), SL = spiral ligament, TC and CANOPY = tectal cells and tectal canopy, TM = tectorial membrane, ZP and arrows = zona pectinata of basilar membrane containing hyaline mass, ZT = zona tecta of basilar membrane. omys, Perognathus, and Chaetodipus are each similar and intermediate to the ex- tremes. The variation in quantity and dis- tribution of hyaline material is striking from base to apex and it seems reasonable to pre- dict that these changes affect the vibratory characteristics of the basilar membrane (Fig. 11). Pye's (1965) observations on Hetero- mys suggest that the distribution of hyaline material in the zona pectinata is similar to that observed for Liomys. The basilar membrane is narrowest (± 100 )um) at the beginning of the first half turn of the cochlea in all genera (Webster and Web- ster, 1977). In Dipodomys and Microdipo- dops, the width doubles in the first half turn and increases less rapidly thereafter to a maximum of 241 and 254 jum, respectively, until it declines slightly in the apical turn. Width increases dramatically in Perogna- thus and Chaetodipus to reach a maximum of about 150 Aim at the end of the first turn beyond which it decreases slightly to the apex. Liomys shows a slight and uniform increase from 110 )um basally to a maxi- mum of 160 )um at the end of the second turn and decreases slightly to the apex (Webster and Webster, 1977). In compari- son, the basilar membrane of the bat, Pter- onotus parnellii, varies in width from ca. 40 Aim at the base to ca. 112 ^im at the apex. Relative width shows the same pattern among the heteromyid genera as described above for relative thickness. As a group the several cell types which lie on the
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