. Journal of morphology . al connection with it (cf. Fig. 2,and Plate I, Figs. C and D, ad). In connection with the opening of the duct of the gland the con-formation of the nasal cavity must be understood. From the externalnaris the nasal passage extends at first somewhat mesially, thenalmost directly posteriorly for a short distance, the longer diameterof its lumen having in this region a horizontal position. In the The Lateral Nasal Glands of Amphiuma. 145 region where the dnct of the lateral gland oj^ens into it, however, thenasal passage makes an abrupt twist, so that the longer diameter
. Journal of morphology . al connection with it (cf. Fig. 2,and Plate I, Figs. C and D, ad). In connection with the opening of the duct of the gland the con-formation of the nasal cavity must be understood. From the externalnaris the nasal passage extends at first somewhat mesially, thenalmost directly posteriorly for a short distance, the longer diameterof its lumen having in this region a horizontal position. In the The Lateral Nasal Glands of Amphiuma. 145 region where the dnct of the lateral gland oj^ens into it, however, thenasal passage makes an abrupt twist, so that the longer diameter ofthe lumen takes a vertical position (cf. Figs. 1 and 2). A shortdistance posterior to this point the olfactory epithelium begins, theportion of the passage anterior to this point serves, then, as an intro-ductory passage comparable to that described by Bruner 01, andSeydel 95, in larvaB of various urodeles (e. g., Triton and Ambly-stoma), by Wilder Ola, in Siren, and by Hinsberg 01, in larval anu-rans and in urodeles. V. Fig. 2.—Transverse section somewliat posterior to Fig. 1. x 1^ 2/3. Ab-breviations : ad, atrophied duct; ci, cross section of the constrictor musclenear its insertion; co, cross section of the constrictor muscle near its origin;cdl, cross section of the dilatator muscle; d, duct of the lateral nasal gland;Ic, longitudinal section through the body of the constrictor muscle; Ig, lateralgland; na, nasal capsule; ne, nasal epithelium; n, nerves; P, portion of thepremaxillary bone; v, blood vessels. The twisting of the nasal passage in its transition from intro-ductory to olfactory regions involves a thickening in the wall of thepassage. This thickening begins anteriorly in the mesial wall and,gradually increasing, extends spirally around the cavity, ending inthe lateral wall. It results in the occurrence upon the inner surfaceof the cavity of a spiral fold or ridge following the course of thethickening. Upon the forward directed surface of this fold the ductof
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