278 H. H. WILDER, 



differ in several not unimportant particulars, Necturus representing 

 the simpler form. 



Necturus maculatus. 



The cartilages consist of flattened pieces situated upon either side 

 of the rima glottis, and showing the most marked individual variation, 

 dependent apparently upon age, size, breadth of body and amount of 

 muscular development (PI. 19, Figs. 1— -7). 



The typical form is best seen in young individuals (Figs. 1 and 2), 

 in which the cartilages consist of a single pair (the Cartilago lateralis 

 of Henle) composed of an anterior triangular portion and a long 

 posterior process. The triangular piece is solid, with entire edges, 

 and often possesses a curved process depending from its lateral 

 (outer) angle. The posterior process is curved outwards, and apt to 

 be somewhat widened near its free end. These processes are not 

 applied to the side of the trachea, and do not reach beyond the 

 laryngeal region (Fig. 8). Older and larger specimens show irregular 

 notches in the margin, foramina, and even isolated bits of cartilage 

 which show every appearance of having become detached from an 

 original single piece. This phenomenon finds its most probable cause 

 in the tension exerted upon a thin and delicate plate by the gradual 

 growth of underlying parts, closely connected with it; especially as 

 one sees by careful examination of the series here figured, that the 

 loss of continuity occurs in what would be the narrowest and weakest 

 spots of the original cartilage. The almost complete integrity of the 

 largest one of the series (Fig. 7) may be explained by the powerful 

 structure of the individual from which the specimen was taken, the 

 strength and thickness of the plate having proved capable of resisting 

 the force of the muscular growth. The specimens here figured, and 

 from which these deductions were taken, were prepared with the 

 Methyl-blue method mentioned in the introduction, which stains only 

 adult hyaline cartilage. Kxamination of the specimens under a low 

 lens often demonstrates the preseuse of a dense tissue with scattered 

 cartilage cells, connecting the several parts; that is, the separate 

 hyaline elements lie as it were imbedded in a matrix, which undoub- 

 tedly represents the original piece. In the figures representing 

 the same cartilages in Proteus the unstained portions are also figured. 

 This phenomenon of hyaline and non-hyaline elements is constant 

 among Urodeles and receives a histological explanation under the sec- 

 tion devoted to Amphiuma. In the other cases I shall merely refer 

 to the two sorts of tissues without farther explanation. 



