34 



NORR/S. 



is seen the beginning of the partition {pe) described by Villy in the frog as separat- 

 ing utriculus from sacculus. 



Figs, io and ii. Similar sections of a somewhat older larva. Both sections are 

 through the posterior part of the vesicle, Fig. ii being the posterior of the two. 

 In Fig. IO is seen the beginning of the pars neglecta in intimate relation with the 

 lagena. Fig. Ii shows the true partition between utriculus and sacculus {us) in con- 

 tradistinction to the partition between posterior canal and horizontal canal (pe), the 

 beginning of which was shown in Fig. 9. In Fig. 10 part of the otic cartilage is 

 shown. 



Fig. 12. Similar section of a larva in the siredon stage, about 30 mm. in length. 

 The otic capsule is completed. The two sacci endolymphatici have nearly met above 

 the brain. 



Fig. 13. Similar section of same larva posterior to preceding, through pars neg- 

 lecta. 



Fig. 14. Similar section of same larva posterior to preceding, passing through the 

 lagena. The beginning of the pars basilaris is seen as a dorsal extension of the dor- 

 sal wall of the lagena. 



Fig. 15. Similar section of auditory capsule of an adult, passing through the 

 lagena and the pars basilaris. Some of the parts have been slightly displaced from 

 their original location through the reagents used, and by a mistake the perilym- 

 phatic chamber has not been figured. 



Fig. 16. Reconstruction in wax of the cavity of the left auditory vesicle, repre- 

 sented in Figs. 6 and 7. Anterior view. 



Fig. 17. Similar reconstruction of vesicle represented in Figs. 8 and 9. Ante- 

 rior view. 



Fig. 18. Similar reconstruction of vesicle represented in Figs. 10 and 11. a me- 

 sal, b lateral view. 



Fig. 19. Similar reconstruction of vesicle of a larva about 15 mm. in length. 

 a mesal, b lateral view. 



Fig. 20. Similar reconstruction of vesicle represented in Figs. 12-14. a mesal, 

 h lateral view. 



Fig. 21. Projection upon a plane surface of the sensory epithelium of the auditory 

 vesicle represented in Fig. 5. 



Fig. 22. Similar representation at the stage of development shown in Figs. 6, 7, 

 and 16. 



Fig. 23. Similar to preceding, at period shown in Figs. 8, 9, and 17. 



Fig. 24. Similar to preceding, at period shown in Figs. 10, 11, and 18. 



Fig. 25. Similar to preceding, at period shown in Fig. 19. 



Fig. 26. Similar to preceding, at period shown in Figs. 12-14, ^^^ 20. 



Fig. 27. Similar to preceding, adult condition. 



