. The elasmobranch fishes . Fig. 231. Sagittal section of developing nasal pit, Acanthias. (From Berliner.) , Schneiderian folds. DEVELOPMENT OF OLFACTORY ORGAN We may now notice briefly the development of the olfactory organ in the Elasmobranchs. As is common for vertebrates in general this organ first ap- pears as a thickened epidermal placode or plate which early pits in from the outside toward the brain so as to form a shallow vesicle. By further growth this vesicle sinks deeper and forms a blind sac (fig. 231) in which arise the Schneiderian folds () of the primary and secondary t
. The elasmobranch fishes . Fig. 231. Sagittal section of developing nasal pit, Acanthias. (From Berliner.) , Schneiderian folds. DEVELOPMENT OF OLFACTORY ORGAN We may now notice briefly the development of the olfactory organ in the Elasmobranchs. As is common for vertebrates in general this organ first ap- pears as a thickened epidermal placode or plate which early pits in from the outside toward the brain so as to form a shallow vesicle. By further growth this vesicle sinks deeper and forms a blind sac (fig. 231) in which arise the Schneiderian folds () of the primary and secondary types. Furthermore these folds have produced from their sides numerous accessory folds in which are found the olfactory sense-cells above mentioned (fig. 230). The two divi- sions of the olfactory nerve put these two areas of folds into communication with the olfactory luill), but each division of the nerve may be connected with both of the areas of the folds. Gustatory or Taste Organs Taste buds are present in the Elasmobranchs often in considerable numbers. These are located in the buccal cavity and pharynx and are distributed over the floor and tongue, along the sides, and over the roof of both cavities. An in-
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