Journal of morphology . all, the ear saucer sepa-rates from the sensory band whichis thus cut in two parts, an anteriorbelonging to the VII, and a posteriorlying in the territory of the separation is indicative of anearlier condition of independence,which has been obliterated by theshortening and modifying in otherways of the ontogenetic investigator observed epithe-lial ridges similar to those de-scribed by Kupffer in Petromyzonin the territory of the V, but heconcluded that they were not re-lated to the canal organs of theadult. The early history of the develop-ment of
Journal of morphology . all, the ear saucer sepa-rates from the sensory band whichis thus cut in two parts, an anteriorbelonging to the VII, and a posteriorlying in the territory of the separation is indicative of anearlier condition of independence,which has been obliterated by theshortening and modifying in otherways of the ontogenetic investigator observed epithe-lial ridges similar to those de-scribed by Kupffer in Petromyzonin the territory of the V, but heconcluded that they were not re-lated to the canal organs of theadult. The early history of the develop-ment of the Elasmobranch auditorycapsule does not differ materiallyfrom that of other forms except inthe rate of growth. In this respectit is a much more favorable objectfor the study of the development ofthe internal ear than any other ver-tebrate with which I am 17 shows the auditory area ofthe skin after it has assumed the saucer shape, this conditionof the organ following on the preliminary thickening of the. Cut jy. — The head of an embryoShark (^Acanthias vulgaris), fromnature, magnified 20 times. Thefigure shows tlie saucer-shaped de-pression containing the insinkingsense organ which is to be con-verted into the auditory sense organsof the Shark. Auditory saucer (vesicle). ep Epiphysis. f Fore-brain. g Gill region. /. ! Upper and lower hind-brain region. ni Mid-brain. No. I.] THE VERTEBRATE EAR. 175 ectoderm and its sinking to the bottom of the saucer-like depres-sion. The whole process of the formation of this cup is an exactrepetition of the formation of a canal organ, and its canal as seenin Amia, or of the formation of an ampulla and its canal in theSalmon. As the saucer sinks below the surface, the opening onthe surface grows smaller, the bottom of the saucer increases insize, and the resulting structure is an auditory vesicle distinctlyflask-shaped. The neck of the flask grows longer, and finallyappears bent backwards and inwards by the increase in si
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Keywords: ., bookauthorwistarin, bookcentury1800, bookdecade1890, bookyear1892
