. Journal of morphology . caudal third andfinally tapers to a point. In that portion of the ear capsule formingthe caudal margin of the fenestra there is a pronounced prominencewithin which there is a continuation of the perilymphatic cavity ofthe ear (Fig. 20). Wliile complete developmental stages have not been studied, sec-tions through the head of a larva soon after hatching, a transform-ing individual and an adult furnish some data regarding develop-ment. In the youngest larva the fenestral plate is relatively smaJ The Columella Auris in Amphibia. 597 and free from the ear capsule all roun
. Journal of morphology . caudal third andfinally tapers to a point. In that portion of the ear capsule formingthe caudal margin of the fenestra there is a pronounced prominencewithin which there is a continuation of the perilymphatic cavity ofthe ear (Fig. 20). Wliile complete developmental stages have not been studied, sec-tions through the head of a larva soon after hatching, a transform-ing individual and an adult furnish some data regarding develop-ment. In the youngest larva the fenestral plate is relatively smaJ The Columella Auris in Amphibia. 597 and free from the ear capsule all round. Although closely associatedwith, it appears to be wholly outside of, the fenestral membrane. At transformation the columella is fused in front with the earcapsule and just fills the opening. Below and behind the columellaa portion of the floor of the ear capsule becomes greatly thickened,especially in its lateral half, which is almost completely separatedfrom the capsule (Fig. 19). In this stage there are a few muscle. Fig. 19. Amphiuma means, transforming larva. (7., arteria carotis in-terna ; , cavum perilymphaticum; Sq., os squamosum; , vena petroso-lateralis; , a portion of the musculus intertransversarius capitis in-ferior. fibers partly differentiated off from the M. intertransversarius capitisinferior which have a slight attachment to this portion of the earcapsule. This portion of the floor of the ear capsule which was thickenedand partly separated off in the transforming individual is in theadult very much thickened, forming the pronounced prominence whichencloses an extension of the perilymphatic cavity as shown in The M. intertransversarius capitis inferior comes into closerelation with the prominence of the adult, but there is no differentia-tion of a distinct opercular muscle. 598 B. F. Kingsbury and H. D. Reed. By comparing Fig. 11 and Fig. 31 (PI. Ill) of Ambystomaand Fig. 50 (PI. VII) of Triton it is evident that this portionof the ot
Size: 1559px × 1602px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookautho, bookcentury1900, bookdecade1900, booksubjectphysiology
