Terry — Th« Nasal Skeleton of Amhlystoma punctatum. 117 



crest never grows high and the dorso-mesal bar joins 

 neither it nor the trabecula to form the boundaries of 

 an olfactory foramen; still the nerve passes between the 

 bar and the trabecula and in front of the crest. The for- 

 mation of the nasal capsule in Rana up to the point so far 

 considered seems to me not fundamentally different from 

 that of Amblystoma. The specialized nasal sac of Rana is 

 provided with a highly specialized and complicated nasal 

 capsule such as is not encountered at any time of life in 

 Amblystoma. There are however some features in these 

 capsules which I believe can be drawn into comparison but 

 first it will be necessary to compare the parts about which 

 the capsule in each case is adapted. 



As stated in the beginning of this paper the nasal sac of 

 Amblystoma is at first a simple ovoid body with a narrow lumen, 

 becoming later complicated by the development of diverticula, 

 one of which is Jacobson's organ. Another much smaller 

 pouch grows out of the lateral side of the main-sac and re- 

 ceives the nasolacrimal duct. The maiu-sac and its diverticula 

 are shown in figure 4. 



The main-sac of the Urodela is in all essential respects 

 comparable with the upper blind-sack of the Anura. The 

 lateral pouch of Amblystoma is indicated as the possible 

 homology of the lateral diverticle of the tadpole by Bawden 

 while Seydel compares only that part in each group which re- 

 ceives the tear-duct, regarding the anterior blind end in Anura 

 as a special development. Seydel homologizes the inferior 

 blind-sac of the frog with the Jacobson's organ of the 

 Urodeles, and points out the absence of this organ in fishes 

 and the Dipnoi, as well as in Proteus and Menobranchus and 

 its primitive state in Amphiuma and Menopoma. 



Besides the roof cartilage of the hinder division of the 

 main-sac which is described on P. 414 of Gaupp's work ('93) 

 and which has already been mentioned in the comparison 

 with Amblystoma, a separate chondrification of the perirhinal 

 tissue anterior to this is described which later joins with the 

 first roof cartilage and also grows around the medial side of 

 the upper blind-sac to form its mesal wall. Roof and mesal 

 wall are continuous in the anterior half of the nasal capsule 



