The Smooth Facial Muscles of Anura and Salamandrina. 329 



the formation of the muscle Anlage. Corresponding to this origin, 

 this Anlage consists, in the stage under consideration, of stellate cells, 

 which resemble the surrounding mesenchyme cells, but are to be 

 distinguished from them by their crowding together, by their more 

 rounded nuclei, and by their active division. This muscle Anlage 

 lies against the posterior wall of the introductorj^ passage of the nose, 

 internal to the invagination of the glandula nasalis externa, whereby 

 the position of the constrictor naris is clearly indicated. However, 

 the separate nasal muscles are not yet distinguishable. Behind the 

 muscle Anlage the lacrymal duct opens already into the nasal cavity. 



In a Triton larva thirty-one millimeters long we find the above 

 conditions wholly changed. From the now fully developed car- 

 tilaginous nasal capsule arise all three nasal muscles, of which the 

 constrictor naris and dilatator naris are approaching a functional 

 condition, and are composed chiefly of the usual smooth muscle cells. 

 On the surface of the muscles, however, lie certain cells which have 

 not yet completed their metamorphosis, and which still possess a 

 number of slender processes derived from the stellate cells of the 

 mesenchyme. 



2) Amblystoma tigrinum. As Wilder (54) and Seydel (45) have 

 reported, the nasal cavity of Amblystoma tigrinum is provided in the 

 larval condition with a sort of vestibule which is wanting in the 

 adult animal. This vestibule corresponds to the introductory passage 

 of the Triton larva, but is distinguished from that passage by its 

 oblique direction through the nasal wall, by reason of which it is 

 bounded externally by a fold of skin, while its floor is the carti- 

 laginous nasal capsule. The inner end of this vestibule leads through 

 the anterior end of the fenestra rostro-lateralis into the nasal cavity 

 and corresponds, therefore, to the external naris of the adult. At this 

 point, then, we should expect to find the earliest indication of nasal 

 muscles, which first appear in an eighty millimeter axolotl with 

 fully developed gills. In this specimen occurs, behind the nasal 

 opening, the Anlage of the constrictor naris, and farther lateral, the 

 Anlage of the dilatator naris accessorius, which in this species is 

 more strongly developed than the dilatator naris and therefore 

 appears earlier than that muscle. These Anlagen consist in each 

 case of a small mass of cells, whose size plainly indicates a young 

 stage of muscle development; however, the condition of preservation 

 of my material does not permit a detailed description of the cells 

 composing these masses. In an axolotl one hundred and two milli- 



