DEVELOPMENT OF BAR AND AOCOESSORY ORGANS IN FROG. 523 
The Development of the Ear and Accessory 
Organs in the Common Frog. 
By 
Francis Villy, 
Owens College, Manchester. 
With Plates XXXIV & XXXV. 
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 develop- 
ment may reasonably be expected to yield. 
Under these circumstances I have, at Professor Marshall’s 
suggestion, 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 compli- 
cated 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 
Eustachian tube and an auditory ossicle, and as such may rea- 
sonably 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 
