- 2 



I. HIGH HOADI.KY. 



The same definite differentiations of the epithelium show well 

 in case 40 B 6. Here, as in the case cited above, both cartilage 

 and epithelium are present. The cartilage is not so extensive, 

 however, but is located near, though not surrounding, the epithe- 

 lial tissues. The relations of the parts of the membranous 

 labyrinth are very much disorganized in this graft, the tissue 



S.Ep 



G.c. 



. mv- 



..... 



;<7 :* * *.*>, . - . - 



FIG. 8. Section of crista acustica of one of the ampullae of a chick of eight 

 days incubation. ( X 235.) G.C., ganglion cells. X.T., nerve tract running 

 from crista to brain. Other abbreviations as in Fig. ~. 



appearing in two places, separated by the host mesenchyme. 

 The character of the cellular differentiation is distinctive. In 

 one of the groups, the differentiation is like that of the ductus and 

 saccus endolymphaticus. These structures are connected, the 

 ductus appearing as a tube leading from the saccus. Xear these, 

 a canal-like formation appears for a few sections These parts are 

 not widely separated from the other group of structures which 

 are adjacent to the mass of cartilage. The parts in this group 

 are in the form of distinct vesicles and tubules, resembling 

 histologically, utriculus, sacculus and a small portion of a canal. 

 In the utricular wall are two areas interpreted as crista? acu>ti-M-. 

 one of which is associated with the canal-like portion already 

 mentioned. 



It would seem therefore, from the data given for the a!o\e 

 cases, that the differentiation of the constituent parts of the otic 

 vesicle is very specific, and that it takes place independent of i he 

 relationships of the various parts, which depend on mechanical 

 factors. 



