THE NASAL ORGANS OF PIPA AMERICANA. 103 



The sensory epithelium is very thick, consisting of cells 

 of an extreme columnar condition. The nuclei are scat- 

 tered at various depths in the basal two-thirds of the cells 

 while the free ends of the cells present the appearance 

 familiar in this region in all Amphibians. 



A little in front of the point of union of the duct of 

 Jacobson's organ with the lateral nasal canal is the open- 

 ing of the duct of Jacobson's gland, fig. 6, jd^ the 

 opening being at the inner angle of the organ. The 

 gland itself, figs. 4 to 8, jV/, lies below the cavum nasale 

 and lateral nasal canal and is on a level with Jacobson's 

 organ. Jacobson's gland, as in other Anura, is situated 

 on the median side of the olfactory organ, and in front it 

 extends laterally beneath the nasal cavities. It consists 

 of convoluted cylindrical tubules lined with cubical or 

 low columnar protoplasm, both nuclei and protoplasm 

 staining deeply. It extends from a point somewhat in 

 front of the planes of fig. 4 to that of fig. 8. Its duct 

 passes from the anterior fourth of the gland to empty 

 into the organ of Jacobson, Plate V. In fig. 4 there is 

 a gland, g, which appears diflerentiated from the rest. 

 It continues forward as a tube, and finally enters into the 

 lateral nasal canal just posterior to the plane of fig. 2. 



Farther forward (figs. 4-7), the lateral nasal canal ex- 

 pands externally into a secondary cavity, hi, which is 

 lined with the same sensory epithelium as the cavum 

 nasale, with which it remains in connection by the nar- 

 rower and much depressed portion of the lateral nasal 

 canal. This latter is lined with undiflferentiated low 

 columnar cells. More anteriorly, the secondary cavity 

 gradually bends downward and inward so that its anterior 

 resfion comes to lie below and in the median line of the 

 rest of the olfactory apparatus as shown in Plate V. 



From the anterior end of the lateral nasal canal the 

 nasal canal continues forward as a flattened tube to the 



