648 FRANCIS M. BALDWIN 



of the gland), the origin of the cells of which is difficult to deter- 

 mine. The exact extent of the anlage is difficult to determine, but . 

 it is about 150 micra long. Just caudad and somewhat medial, 

 the ventral portion of the second branchial pouch extends down- 

 ward, separating the first and second branchial cartilages >om 

 each other. A similar ventral portion of the first branchial pouch, 

 separates the hyoid and first branchial arches. 



The anlage of the first epithelial body in this stage (e.6.i, fig. 39), 

 is an irregular longitudinal tract of entodermal cells, of consider- 

 able length (a remnant of the ventral portion of the third bran- 

 chial pouch) , lying between the cartilages of the second and third 

 arches. The cephalic end of this sheet is about 700 micra caudad 

 to the carotid anlage, and lies just back of the point where the 

 second afferent brancl^al artery enters the second gill-arch. The 

 caudal limit is difficult to determine. 



The anlage of the second epithelial body (e.6.2, fig. 39), is a 

 similar tract of entodermal cells lying between the cartilages of the 

 third and fourth arches, the cephalic end of which lies just caudad 

 to the point where the third afferent branchiaj artery enters the 

 third gill-arch. The cephalic end of this anlage is 360 micra 

 caudad to the cephalic end of the first, but the anlagen of both 

 bodies parallel one another, so that in transverse section the 

 cephalic end of the second is cut with the caudal end of the first. 



Maurer ('88) in describing these structures in Triton, was 

 unable to find any trace of the carotid gland in the early stage of 

 metamorphosis. He describes however, the anlagen of the epi- 

 thelial bodies. ''Auf Querschnitten zeigte sich zwischen dem 

 zweiten und dritten, so wie zwischen dem dritten und vierten noch 

 vcrha^idenen knorpehgen Kiemenbogen die Reste der vierten 

 und fiinften Kiemenspalten in Form unregelmassiger langlicher 

 Gebilde, die sich aus Epithelzellen zusammensetzen und nur 

 durch Aneinanderlagerung und Schrumpfung der Kiemenplatten 

 entstanden sein konnen." It is possible that the Amblystoma 

 larva of this stage in my material is somewhat farther advanced in 

 its metamorphosis than was that of Triton described by Maurer. 



In the late transforming larvae the gill region has been so far 

 modified that it is similar in many respects to the adult condition. 



