112 Trans. Acad. Sci. of St. Louis. 



integral part of the nasal capsule. In considering this par- 

 ticipation in the nasal skeleton, it must be remembered th at 

 the nasal sac has grown backward into the region of the 

 antorbital process. Special relations of the antorbital pro- 

 cess to the nasal skeleton of Amblystoma are developed 

 rather late. 



The trabecular horn is, from the first stage on placed ven- 

 trad of the anterior end of the nasal sac and Jacobson's organ. 

 To the latter, the tip of the horn seems specially adapted, 

 conforming closely to the curves of its inferior surface. The 

 relation which this broad plate of cartilage holds to the roof 

 of the mouth must, of course, be thought of in studying its 

 development. 



The anterior trabecular plate supports the cephalic end of 

 the brain, mainly the olfactory bulbs. It appears to have its 

 origin in the medial processes of the trabecula and from its 

 earliest appearance through all stages studied holds a posi- 

 tion beneath the olfactory bulbs. It acquires connection 

 with the ethmoidal plate secondarily. The latter, it will be 

 remembered, has its beginning in the ethmoidal processes of 

 the rods (Col. eth.) The association of the trabecular plate 

 with the olfactory region of the brain may be taken to indi- 

 cate a special relationship between them, a view which is 

 supported by its secondary connection with the ethmoidal 

 plate, resulting in the perfection of the ethmoidal skeleton in 

 front of and below the olfactory bulbs. I am inclined to re- 

 gard the anterior trabecular plate as the floor for the olfac- 

 tory region of the brain and look upon it as a special part of 

 the ethmoidal skeleton but without denying its adaptation 

 also to the mouth. That it does form a solid roof for the 

 mouth in front and brace the trabeculae is of great impor- 

 tance, especially in some forms ;such as Rana with its long 

 larval period as Gaupp ('93) has said, but I look upon these 

 funtions as subordinate to the ethmoidal skeleton function in 

 Amblystoma. 



The anterior trabecular plate has nothing to do with the 

 origin or subsequent development of the so-called nasal 

 septum of Amblystoma ; this develops in connection with the 



