236 AVA^JiS. [Vol. VI. 



foreshadowed in the disappearance of the crista abortiva and 

 the papilla lagense, both of which "disappear" by failing to 

 appear in the development of the ear of those forms lacking 

 them, and they consequently are to be comited in as members 

 of the organ complexes forming these so-called auditory maculae. 

 Now extending this process further, guided by abundant indica- 

 tions found in the mammalian ear, we find the cristas acusticae 

 anterioris and horizontalis failing to bud off from the macula acus- 

 tica utriculi and the crista acustica posterioris remaining in the 

 macula acustica sacculi along with its abortive sister organ. Thus 

 the sense organs of the ear located in the parts first developed 

 in point of time and present in even the lowest forms above the 

 Cyclostomes are reduced to the Cyclostome type, and unless 

 some new need of the organism calls upon the declining maculas 

 and revivifies them, we may expect them to become more and 

 more undeveloped, until finally the cochlear organ alone will 

 seem to be a product of the auditory involution as represented 

 in the adult anatomy, while for a time the rudiment of the 

 canals and later of the sacculus and utriculus in something of 

 their pristine independence will appear as ontogenetic struc- 

 tures whose significance will hardly be understood if our litera- 

 ture shall have failed our descendants. That this condition of 

 things is in the remote future goes without saying, but that in 

 essentials the above picture is trustworthy cannot be doubted 

 by those who believe in the law of evolution and the manifesta- 

 tions of its workings presented to us in the story of the origin 

 of the vertebrate ear and its manifold transformations down to 

 the present time. 



As regards the modifications of the accessory acoustic appara- 

 tus, I have nothing to add to the little already given. I have 

 paid but slight attention to its history, mainly because it is not 

 essential to the acoustic function and also because it lies beyond 

 the limits of, and in no way influences the conclusions of this 

 study. 



