572 
b) Results of a comparative-anatomical study. 
As my results differ in many cases from former work, and as 
my comparison of all the forms investigated has led to somewhat 
different views, I will make the following statements: 
1) Typically, Amphibians possess two pairs of respiratory carti- 
lages, an anterior pair placed at the sides of the opening of the 
glottis, and a pair posterior to these lying, along the sides of the trachea. 
The former bear the vocal cords when present, and may be termed 
Fig. 1. Diagram of an Amphibian larynx. ary. Arytaenoid cartilages. 
te. Tracheal elements. 2.£. Intrinsic muscular ring. Z’r.7r’. Different elements of the 
transverse system. 
from now on the Arytaenoids; while the latter pair, containing as 
they do, not only the future Cricoids but the tracheal rings as well, 
are best called simply tracheal elements. 
2. This typical arrangement is found in most Urodeles, the 
main differences lying in the length of the tracheal elements, which 
are dependant upon the relative length of the trachea. (Compare 
Amphiuma and Triton.) 
The principal modifications of this plan are as follows: 
In Proteus and Necturus only one pair is present. HENLE 
supposes this a primitive condition, as above mentioned, but it seems 
more probable that here a secondary reduction of parts has taken 
place, either by fusion or by elimination. Later researches, especially 
embryological, must determine this point. 
In many of the higher Anourans the tracheal elements suffer 
consolidation across the median line, thus forming a sort of Cri- 
coid. This fusion takes place, however, only anteriorly, the remaining 
