STUDIES ON THE DEVELOPMENT OF THE EAR 

 OF AMBLYSTOMA. 



Part I. : Development of the Auditory Vesicle. 



H. \V. NORRIS. 



The present paper is the first of a series that the writer 

 hopes to publish on the development of the Batrachian ear. It 

 contains the results of studies on the development of the audi- 

 tory vesicle in Amblystoma. The species studied was for the 

 most part probably A. jejfcrsoiiiaimm, but part of the material 

 was of A. piinctatum. The writer is under great obligations to 

 Professor J. S. Kingsley, of the University of Nebraska, under 

 whose direction these studies were pursued, for his criticism and 

 assistance in many ways. The preparations studied were largely 

 those loaned by him. Through the kindness of Professor S. H. 

 Gage thanks are due the Anatomical Department of Cornell 

 University for part of the material used. 



Serial transverse, horizontal, and sagittal sections were stud- 

 ied. Reconstructions in wax from serial sections were made of 

 many of the more important stages. The reconstructions, how- 

 ever, represent merely the cavity of the ear vesicle. Upon the 

 finished wax models were painted section by section the out- 

 lines of the sensory epithelial patches. Figs. 18-22 are draw- 

 ings of reconstructions. Figs. 23-29 are projections upon a 

 plane surface of some of the stages in the development of the 

 sensory epithelium. Figs. 1-17 are camera lucida drawings of 

 transverse sections. 



This paper is merely descriptive and in no sense intended to 

 be comparative. As the literature bearing directly upon the 

 development of the ear of the Urodela is not extensive, a bibliog- 

 raphy will be withheld for a future paper. Unfortunately the 

 writer has not had access to the work of Retzius.^ The studies 

 on which this paper is based were pursued in the morphological 



1 Das Gehorogan der IVirbelthiere, Stockholm, 1881-84. 



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