The Amphibian larynx. 287 



5. Mana, 



Nowhere among the limits of a genus or even of a family is 

 there so great diversity of structure as here. They may be arranged 

 in three types, the differences of which may be explained by com- 

 parison. 



Type I (Figs. 38—41). This type appears to have but one re- 

 presentative, Rana temporaria of Europe, even the allied R. sylvatica, 

 often considered a sub-species of the first, conforming rather to the 

 second or general type. It is the most embryonic and may be con- 

 sidered as a permanent retention of a stage passed by other frogs 

 during the metamorphosis. The arytaenoids are huge cartilages which 

 in general shape may be compared to spherical lunes of 90 ** placed 

 together with their concave surface directed inwards and downwards. 

 Their longest axis is transverse (Fig. 40) and the vocal chords in the 

 inside are parallel to this axis (Fig. 41). From their apex which is 

 directed upwards and somewhat prolonged are segmented oft' those 

 tiny elements known as the cartilages of Santokini. As this is 

 })lainly a mistaken homology, there being no possible relationship be- 

 tween these flecks occurring in this specialized family and the Mam- 

 malian cartilages of this name, I may suggest the term apical 

 cartilages to replace the old name. The annulus has become 

 complete by the formation of a delicate isthmus connecting the two 

 cardiac processes at their base. These latter have fused above with 

 the arytaenoids (Fig. 35). The body of the annulus lies in a trans- 

 verse plane perpendicular to the longitudinal axis of the body. The 

 bronchial and posterior pharyngeal processes are easily distinguish- 

 able although the latter is not a simple loop but a rather short and 

 thick process. Upon the sides of this a pair of new processes, the 

 anterior pharyngeals, project forwards from the annulus and 

 furnish origin for some of the intrinsic muscles. 



Type II. This is the usual form for Rana and includes every 

 other species investigated except R. esculenta. The figures to illustrate 

 this type (Figs. 31—35) I have taken from the common American 

 grass frog, R. virescens, which is figured in details to show muscu- 

 lature. This does not appear to differ essentially in the three types 

 under discussion which refer merely to the cartilages. In order to 

 derive this type from the first, it is only necessary to imagine a 

 rotation of the arytaenoids about their transverse axis for about 90° 

 toward their pharyngeal side displacing their adjacent parts in pro- 

 portion to their proximity and closeness of relation. This rotation 



