Terry — The Nasal Skeleton of Amhlyttoma punctatum. Ill 



(A) The primary position of the rod (Col. eth.) of the 

 13 mm. larva (a) in the membranous cranial wall of the eth- 

 moidal region, (b) over the olfactory nerve and (c) in close 

 relation to both the olfactory bulb and nasal sac ; (B) its sec- 

 ondary connections and changes through growth in adaptation 

 to the olfactory organs, — these things indicate, I believe, a 

 direct relationship between the rod and the latter structures. 



In its further development it has been noticed how 

 the cartilage spreads in two directions : toward the central 

 olfactory organ on the one hand and about the periph- 

 eral organ on the other. The ethmoidal processes, bridge and 

 finally the ethmoidal plate are adapted to the fore part of cen- 

 tral olfactory region, while the rod itself with its hooked end 

 is applied to the olfactory bulb laterally and caudally. The rod 

 also covers the olfactory nerve in its short course between 

 the nasal sac and the brain. Through the formation of car- 

 tilage growing laterally into the perirhinal membrane (lateral 

 process and medial nasal process) a roof and side wall are 

 given to the nasal capsule. 



The relations of the Crista trabeculae to the nasal organs I 

 regard as wholly secondary since they are brought about in 

 the ontogeny of Amblystoma by disproportion in the rate of 

 growth of these parts. In the youngest stage the crest took 

 no part in the skeleton of the ethmoidal region and it is only 

 in later stages of development when the nasal sac and olfac- 

 tory bulb have increased in size that it affords a protection 

 for them. 



The antorbital process, it was noticed, occupied a position 

 between the eye-ball and the internal naris in the first stage 

 described. The anlage of this process is in connection with 

 the trabecula to which the independently forming cartilage 

 later extends. The process projects from the trabecula at the 

 level of the anterior edge of the Crista and therefore behind 

 the level of the olfactory organs. In the early stage I can- 

 not determine that the process is adapted more to the nose 

 than to the eye. In later stages, however, it curves forward 

 and comes in contact with the nasal sac; and finally, entering 

 into the formation of the posterior cupola, it becomes an 



