Bawden, Nose and facobson 's Organ. 143 



Fig. 1, Plate XI, is a representation of a directly dorsal 

 view of the right nasal cavity of a larval European salamander 

 (Salamandra atrd). Essential points of resemblance are immed- 

 iately observed to exist between this European type and Am- 

 blystoma. The model as above figured is enclosed in its carti- 

 laginous investment and so the complete homology is partially 

 obscured; but in fig. 2, Plate XI, which shows the same model 

 from a ventral view the points of resemblance are more 

 fully brought out. Although the exterior shows some 

 difference in general configuration, the European being narrow 

 and thick and rounded, broad and flat and much thinner in com- 

 parison ; yet the relative situations of the different parts are the 

 same. It must also be taken into account that the former is a 

 model of the larval cavity while the latter is a model of the 

 cavity of an adult Amblystoma. The comparison of the invest- 

 mental relations brings out still more markedly the difference in 

 the comparative age of the two specimens (compare Figs. 1-15, 

 Plate V, with in and/.r, Figs. 1, 2, Plate XI). The model of 

 the European salamander is much more highly magnified, abso- 

 lutely, than that of Amblystoma. The internasal plate is not 

 as yet completely united along the median line, while the only 

 one of the external cartilaginous plates which was sufficiently 

 differentiated to be modelled was the pre-maxillary which sends 

 back its overarching process as seen in Fig. I, Plate XI, px. 



There remains to be remarked the correspondence in the 

 position of the curious diverticles which are present in each case. 

 One of these, the nasolachrymal, or, is discussed elsewhere. 

 The other is seen in section, Fig. 1, Plate IX, jd, and is figured 

 upon the model atj'd, Fig. 2, Plate XI. 



From camera drawings upon sheets of wax (the same meth- 

 od has been followed in all) the model figured in Fig. 6, Plate 

 XI, was constructed to show the right olfactory cavity of a 

 young tadpole, larval, body length 5 mm, leopard frog, Rana 

 virescens. At this early stage the nasal sac consists of a gen- 

 eral cavity with its two diverticles and its external and internal 

 nares, od, id, extl and intl, Fig. 6, Plate XI, and Fig. 5, Plate X. 

 The general curvature of the organ from its external to its internal 



