1901.] NATURAL SCIENCES OF PHILADELPHIA. 459 



of that side, and thus lies between that passage and its nasal 

 glaud. The section is cut posterior to the opening of the right 

 nasal gland, r-.n.g., into the right nasal passage, r.n.c. The left 

 side of the section passes through the opening of the left nasal 

 gland, l.n.g., into the left nasal passage. 



In the next section (fig. 2/) the complexity of the nasal appar- 

 atus has, apparently, considerably increased. In the first place, 

 the ventral portions of the nasal cartilage, which, anterior to this 

 point, formed a more or less complete wall ventral to the nasal 

 passages, have disappeared, and on the right the dorsal portion of 

 the'cartilage has separated from the median, s., and is now repre- 

 sented by a short straight piece, n.c'., and a long curved piece, 

 n.c, enclosing a part, c, of the right nasal passage. On the left 

 the dorsal, wall of cartilage is still connected with the median sep- 

 tum. The nasal passages are here of quite different shape from 

 what they w^ere in the preceding section. They are still more 

 •elongated in a dorso-ventral direction, and that on the right, 

 which is nearer the base of the snout, is cut at the point, v. p. , at 

 which it opens ventrally into the narrow ventral passage, which, 

 in turn, leads posteriorly to open at the posterior nares. d. repre- 

 sents a narrow diverticulum, projecting in a ventro-lateral direc- 

 tion, which may be followed almost to the jiosterior end of the large 

 dorsal passage. ,A large branch of the main nasal passage, r.n.c, 

 is represented at c, and the following section passes through the 

 point at which this lateral passage opens ventrally into the main 

 passage. 



On the hift side of the section is seen the left nasal gland, l.n.g., 

 cut posterior to its opening into the left nasal passage. On either 

 side of the ventral end of the median cartilage, s., is seen a small 

 collection of cells, j., which, according to Rose, is the rudimentary 

 Jacobson's organ. These two collections of cells, which will be 

 spoken of as " Jacobson's organ," extend from this point poste- 

 riorly for a considerable distance, as two solid rods of cells; they 

 then become hollowed out to form tubes, which soon open ven- 

 trally into the ventral nasal passages, v.j). , as will be shown in one 

 of the following figures. The section represented in fig. 2/ passes 

 near the extreme anterior end of Jacobson's organ. 



In fig. 2g, which is only a short distance posterior to the one 

 just described, Jacobson's organ is still seen as two solid rods of 



