The Amphibian larynx. 307 



a) The transverse band. 



This element is clearly the Dorso-branchialis 5 (D^) of the dia- 

 gram (see Fig. A). During development it remains in its simple 

 condition until the thyroid process of the hyoid complex, by its 

 downward growth, comes in contact with it. This separates the muscle 

 into two portions of which the inner segment alone remains a laryn- 

 geal muscle, the Dilatator aditus laryngis (t), described by 

 Henle as the "Oeffner des Stimmladeneinganges". The outer portion 

 becomes the 4'^ Petro-hyoid, which always occurs in close con- 

 nection with the former (Fig. 31). After the formation of the carti- 

 laginous annulus, the upward growth of the anterior pharyngeal pro- 

 cesses, coming in contact with the lower surface of the Dilatator, 

 cause a separation of a few of its lower fibres, which ditferentiate as 

 a pair of accessory slips, seen in Fig. 32 {f and t"). 



Of these two secondary slips Göppert has described the inner 

 one, extending between the anterior pharyngeal process and the ary- 

 taenoid, but has overlooked the outer one. Of the first he has 

 suggested its secondary connection with the "cricoid". "Ferner sehen 

 wir, dass der Dilatator auf seinem Wege zum Arytänoidrand un- 

 mittelbar an dem sogenannten Cricoid vorbeizieht, und beobachten, 

 dass bereits ein ziemlich beträchtlicher Theil von Muskelfasern am 

 Cricoid Ursprung genommen hat. Bei Larven vor der Metamorphose 

 — es wurde ein Exemplar mit vier Beinen und langem Schwanz 

 daraufhin untersucht — fehlte dieser Cricoidursprung noch gänzlich". 

 In other forms besides Bana, where the anterior pharyngeal processes 

 are not as prominent, the differentiation of these slips does not seem 

 to occur. 



ß) The Sphincter and its derivatives. 



This ring is composed of the elements figured in the diagrams 

 (Figs. A and D) as F, and all the other muscles found in the 

 adult frog larynx may be derived from it. They are thus intrinsic 

 in origin, in distinction from the elements derived from the transverse 

 band (D7) although this distinction does not hold in the adult con- 

 dition of the Anura. The earliest muscular element to diöerentiate 

 from this ring, appears in the region of the anterior (ventral) raphe. 

 This consists of a pair of bundles, at first completely continuous with 

 the ring, the free ends of which extend outwards and downwards, 

 giving the muscle the shape of an inverted-U. In a late larval stage 



Zool. Jahrb. ]X. Abth. f. Morph. 21 



