280 H. H. WILDER, 



lows. The respiratory cartilages consist primarily of a 

 flattened pair homologous with those of Necturus, and 

 consisting as in this latter form, of a triangular piece 

 and a posterior process. While in Necturus the carti- 

 lages are relatively small, and confined to the laryn- 

 geal region, in Proteus the posterior processes become 

 su fficiently extended to reach the lungs. As 'm Necturus, 

 this simple primary piece becomes fenestrated, and 

 irregularly broken, the most constant rupture being 

 that which separates the triangular piece from the 

 pos ter ior process. 



The triangular pieces lying by the side of the rima glottis, may 

 be termed from now on the arytaeuoids, while the term tracheal 

 elements will be found to be generally applicable to the posterior 

 processes and their derivatives. Henle's term, Cartilago lateralis 

 should be restricted to the originally simple piece (as found in young 

 Necturi and presumably in young or larval Protei), from which both 

 elements take their origin. 



3. The remaining Ichthyoidea. 



In this group I include the Perennibranches, Siren and Siredon, 

 and the Derotremes Amphiuma and Menopoma. Notwithstanding the 

 external ditierences in the gill region, they show very similar con- 

 ditions in the respiratory cartilages and may thus be considered to- 

 gether. Of these, Siren, as presumably the most primitive, should 

 furnish the best results, and its embryological development, as yet 

 unknown, will present important facts in this as in other departments" 

 The one I have selected to represent this group is Amphiuma, a 

 matter depending entirely upon the supply of material. I believe, 

 however, that it faithfully represents the group in respect to the 

 matter under discussion. 



Amphiuma tridactylum. 



Owing to the attenuated form of this animal, the respiratory car- 

 tilages have undergone some modifications which allow themselves, 

 however, to be readily derived from the conditions seen in Proteus. 

 An unstained preparation, or one stained in borax carmine, shows 

 what is apparently a continuous piece extending along each side of 

 the trachea from the larynx to the bronchial region, exactly as in 

 Proteus (cf. Fig. 9 with Fig. 15 T.). Anteriorly the already dif- 



