530 LOUISE SMITH 



comparison with methylen-blue preparations, dissections, and 

 other series of this work. 



For comparison, dissections were made of Necturus and 

 Cryptobranchus ; methylen-blue preparations of Diemyctylus 

 viridescens, Amblystoma opacum, and Spelerpes ruber; dissec- 

 tions under the binocular of Spelerpes ruber, adult Amblystoma 

 opacum, and adult Salamandra maculosa; serial sections of a 

 Salamandra larva, Necturus embryos, a small Cryptobranchus, 

 an Axolotl, Typhlomolge rathbuni, and of several stages of 

 Desmognathus fusca were studied. 



At this point, I wish to express my sincere thanks to Dr. H. 

 H. Wilder for his valuable advice and criticism; to Mrs. Wilder 

 for many helpful suggestions and for the use of her specimens 

 and notes on metamorphosis, and to Mr. E. R. Dunn for material 

 from his amphibian collection. 



LARVAL CONDITION 

 1. Hyobranchial skeleton 



The hyobranchial apparatus in the larva of Spelerpes bislin- 

 eatus consists of the hyoid and three branchial arches (figs. 4 

 and 5). The individual arches are not clearly defined, however, 

 as in the lower fishes, for in some instances certain cartilages are 

 missing and in others the exact morphology of parts is doubtful. 

 The apparatus consists, in the main, of paired cartilages which 

 are hung, directly or indirectly, on a single median basal piece. 

 This basal piece or first basibranchial, a rather small, more or 

 less cylindrical cartilage which lies well forward in the midline 

 of the floor of the pharynx, is thus of considerable physiological 

 importance. Anterior and lateral to it, is the pair of ceratohyals, 

 the sole remnants of the hyoid arch. The ceratohyal is a long, 

 heavy cartilage, the largest in the whole apparatus. At its 

 proximal end, it articulates with the anterior end of the first 

 basibranchial and projects posterolaterally to be suspended from 

 the skull by connective tissue at its distal end. 



Ventral to the posterior half of the first basibranchial and also 

 median, is a somewhat triangular, dorsally concave branchial 



