THE DEVELOPMENT OF THE EAR AND ACCESSORY 

 ORGANS IN THE COMMON FROG. 



By Francis Villy, Owens College, Manchester. 



[With Plates XL and XII.] 



The development of the auditory organ of Vertebrates is an 

 embryological subject that has hitherto received very little attention. 

 The ear has been studied more completely in the higher than in the 

 lower types, and mammals have received an amount of notice in this 

 respect altogether out of proportion to the value of the evidence 

 that their highly modified development may reasonably be expected 

 to yield. 



Under these circumstances I have, at Professor Marshall's sug- 

 gestion, undertaken an investigation of the development of the ear 

 of the common frog (R. temporaria), including the associated organs, 

 from the earliest stages to the permanent form. 



The frog's ear has been chosen as a subject for the reason that 

 it probably represents an important stage, more complicated than 

 the simple internal ear of fishes, and lower than the condition found 

 in higher Vertebrates. At the same time the frog may be taken 

 as a type of the lowest class possessing a Eustachian tube and an 

 auditory ossicle, and as such may reasonably be expected to throw 

 some light on the history of these organs during its metamorphosis 

 from tadpole to frog, from typically aquatic to typically terrestrial 

 structure. Besides these advantages possessed by the frog as an 

 animal suitable for study, embryos and tadpoles may readily be 

 obtained at any desired stage, from the egg to the adult. 



