into the descriptions. Secondly, we arc obliged to acknowledge the 



value of the development of the ear in systematical arrangements, 

 when we consider that this organ gradually returns to simplicity in 



the series of the Vertehrata, and that especially in the next class, of 

 Pisces, it obtains systematical importance again. Therefore, t hough 

 not accepting the structure of ear as the first principle for the divi- 

 sion of those animals, I shall combine it with the dentition. 

 Tschudi discredited Midler's observation, vindicating for all A mini 

 Eustachian tubes and a cavum tympani, and only referring variations 

 of the aperture of the Eustachian tuhe in the cavum tympani to the 

 age of the individual {Bombinator igneus). Besides he mentions 

 frequent examinations of the structure of the ear, according to which 

 'his organ, especially among the " JBombinatorida," is liable to 

 variations, nearly in every genus, as regards the form and situation 

 of the ossicula auditus, the chorda tympani, the tympanum, the tuba 

 Eustachii, &c. It is a great pity that Tschudi never published 

 these examinations; but in those which he has published I cannot 

 quite agree with him. 



The imperfect development of ear I have found or recognized in 

 Bombinator igneus, Pelobates fuscus and eultripes, Alsodes tnonti- 

 eola (Wiegmann in Tehnatobius peruvianiui), Micrhyla achat i no*, 

 Phryniscus nigricans, /<cris and cruciger, Brachycephalus ephippium, 

 Hemisus guttatum {Engystoma guttatum, Rapp.), and finally in Rhi- 

 nophrynus dorsalis, which, although not belonging to the Opistho- 

 glossa, may be mentioned on account of the structure of the ear. 

 In all these Batrachians, tympanum and cavum tympani are entirely 

 absent ; the Eustachian tube either is entirely deficient, as I found it 

 in Phryniscus cruciger and Rhinophrynus (and according to Midler's 

 observations, perhaps in some specimens of Bombinator igneus and 

 Pelobates eultripes), or it is only a blind tube without osteum Ivm- 

 panicum. Although I always found in some specimens of the same 

 Bpecies the same development of the Eustachian tubes, 1 do not ven- 

 ture to contradict other observations, according to which these tubes 

 were found more or less accessible ; and Tschudi may be right in 

 Stating a variation to occur with the age. But such a variation as 

 regards abolition certainly would not reach the cavum tympani or the 

 tympanum ; and therefore I hold to the truth of the tact that in the 

 aforesaid Batrnchians this part of the ear is wanting. In Bombinator 

 and l'clnlmti's I have always found the osteum pharyngeum of the 

 Eustachian tuhe open. It is situated quite on the side of the pharynx, 

 is very small and narrow, and accessible only to a thin bristle ; the 

 tube passes mar the united os sphenoideum and petrosum inwards 

 and towards the back, crossing the earotis and the nenUS ragUS. 

 The membrane by which it i- formed becomes gradually i v 



ively thin, and is closed without an aperture mar the fen 

 ovalis vestibuli. This aperture is really ovaL closed b) s cartilagi- 

 nous cover and in direct contact with muscles; the nature of the 



. Tscbttdi'i ' Batrai bU,' p. 1 i. 



