37] THE NASAL ORGAN IN AMPHIBIA— HIGGINS 37 



Knorpelstab, der sich bis in die Mitte des Opticusfensters erstreckt und 

 seinerseits wieder in zwei Theile gespalten sein kann. Eine dichte Zellan- 

 haufung verbindet die einzelnen Stiicke mit einander und mit dem Fort- 

 satze des Quadratum, so dass die betreffenden Elemente wohl als eines 

 Ursprungs aufgefasst werden konnen." The term palatal cartilage is a 

 misnomer at least, for it is evident that the palatine bone, which is mem- 

 brane in origin, could hardly be derived from this cartilase 



The capsule of the older larva, 90 mm. long, (Fig. 33) differs consider- 

 ably from that just described; the greatest change taking place in the more 

 anterior parts. The ossification of many of the covering bones, and the 

 resorption of certain cartilage structures, as well as the chondrification of 

 others, has resulted in a capsule very different from that of any other 

 Amphibian. 



The preorbital and postorbital bands are much as before and need no 

 further description, with the exception of the statement that they are 

 more oblique, from medial and dorsal to lateral and ventral, than before. 

 Through resorption, all connection between the preorbital band and the 

 planum basale has been lost, so that a short caudal process from the planum 

 on each side of the median line is a remnant of a trabecula, all intermediate 

 parts having become ossified. The planum basale is shorter than before 

 and the solum nasale or cornu trabeculae is now more posterior and in line 

 with the caudal margin of the basale, which it unites to the lamina externa 

 as in the early stage. The antero-lateral margin of the planum is more 

 semicircularly excavate than before, and the tips of the trabeculae, extend- 

 ing beyond the basale are more slender, the internasal space between them 

 being wider and deeper. 



The planum verticale (pv), arising from the median line of the basale is 

 wider than before, although not relatively as high. It is continued 

 posteriorly into an elongate cylindrical process which extends backward 

 to the level of the posterior margin of the basale, the dorsal root of the 

 olfactory nerve lying lateral to it; while anteriorly it extends forward into 

 a similar process reaching nearly to the tip of the snout. The alary proc- 

 esses, flanking the median rostrum of the verticale, which were just 

 beginning to chondrify in the earlier stage, have now grown forwards and 

 outwards covering the more anterior parts of the nasal sac and uniting 

 with two lateral processes yet to be described, each forms a partial cupola, 

 incomplete ventrally which protects the anterior ends of the olfactory sac. 

 There is a small foramen near the lower margin of this cupola, through 

 which a branch of the profundus nerve leaves the capsule. 



The lateral wall of the capsule of this older stage is considerably 

 different from that described above. The orbito-nasal foramen, the 

 medial process of the lamina externa and their nerve relations are as before; 

 but ventral to the foramen for the externus branch of the profundus, the 



