f/.m. 



g. m . 



__ _ -^>~~i__ t ~ ~"^ ^_ ~~ _. ~^" 



FIG. 165. TRANSVERSE SECTIONS OF THE NOSE IN VARIOUS VERTEBRATES. 

 A D, Illustrating the various ontogenetic and phylogenetic stages of the Jacob- 

 son's organ of Urodeles. In A its position is niedian, and in D lateral. 



E, Gymnophiona, in which the organ becomes separated from the main nasal cavity. 



F, Lacerta agilis. 



G, Placental Mammal ; I, the same, in longitudinal vertical section. 

 H, Ornithorhynchus. (After Symington. ) 



N, main nasal cavity; jc, Jacobson's organ; c.j, Jacobson s cartilage; y.m, 

 intermaxillary gland ; g.n, nasal gland ; n.o, olfactory nerve ; n.t, trigeminal 

 nerve ; d.n, naso-lachrymal duct; mx, maxilla ; o.d, dumb-bell shaped bone. 



