The Amphibian larynx. 277 



added to 70% alcohol, so as to make a dilute solution about 

 the colour of a deep sky. Into this is thrown the piece to be 

 examined, it does not matter whether the cartilage is exposed or not, 

 and allowed to remain indefinitely. If the piece be taken out after 

 the expiration of twelve hours, and dissected in the ordinary way in 

 70 7o alcohol, all the hyaline cartilage will be found to be stained a 

 deep blue, while the surrounding tissue will be very faintly tinged. 

 In the case of a flat piece, the whole may be pressed between two 

 slides, thrown for a few moments into 100% alcohol, then into tur- 

 pentine, and mounted in balsam. 



As alcohol tends to wash out the colour, the procedures in that 

 fluid must be hastened, but it appears safe in turpentine. I believe 

 that all preparations mounted in this way will eventually fade, but I 

 have several such bearing the date of March '93, which appear still 

 in good condition. If a too strong solution be used, the tissues are 

 stained uniformly, and the diflerential value of the method is lost. 

 Subjecting this to a microscopic test, I find that the eflect is due 

 to the strong affinity for the stain possessed by the hyaline inter- 

 cellular substance; neither embryonal cartilage nor fibro-cartilage 

 where the intercellular substance is of another nature, react difi'erently 

 from tissues in general. 



In cases where I have used sections, I have stained in toto with 

 borax or alum carmine, and cut serially. 



My European material has been in part collected by myself 

 while in Freiburg and is partly due to the generosity of Prof. 

 WiEDERSHEiM. Especially do I wish to thank him here for the 

 two specimens of Proteus examined, which were taken from his 

 private aquarium and forwarded to me in America, My specimens 

 of the rarer American Urodeles, including the small specimens of 

 Amphimna were obtained from the firm of H. H. and C. S. Brimley, 

 of Raleigh, N. Car. 



Part I. Cartilages. 



1. JProteidae, 



These forms furnish a natural group, characterized by the pre- 

 sence of primarily a single pair of respiratory cartilages, which may 

 l)ecome secondarily resolved into several pieces. The two genera 



19* 



