578 
to the shifting of its companion, which at first lies wholly posterior 
to it, then crosses and becomes anterior, then looses its tracheal 
attachment, then its laryngeal, becomes an Interhyoid, and finally 
disappears. There thus remains only the dorso-laryngeus, which 
remains in the Anourans, suffering only the slight modifications ne- 
cessary to accommodate itself to the varied forms of the laryngeal 
cartilages. It arises here generally from the cartilaginous epiphyses 
Lev.arc Il. 
Ds.tr _Levare.W \Levarel., yarcı 
X, Br Re © 0 Caaes 
Ra \ m ‘Ma. 
AryeBrs) Bry Brg Bra Bry Crass 
Fig. 3. Actual condition in Urodeles. (To be compared with fig. 2). Temp. 
Temporalis. Mass. Masseter. digast. Digastricus. 7.m.a. Intermaxillaris anterior (mylo- 
hyoid). i.m.p. Intermaxillaris posterior (stylo-hyoid). Zev.are. J—IV. The four levatores 
arcuum. Ary. Arytaenoid (5th branchial arch). Other references as in fig. 2. 
of the posterior cornua of the hyoid, but retains its insertion to the 
sides of the Arytaenoids. It is simplest in Alytes, where it runs 
transversely across. In Bufo and Rana it curves slightly upwards, 
while in Bombinator it is compelled to curve so much to reach 
the minute Arytaenoids in their extreme anterior position, that its 
course is nearly longitudinal. This muscle has been described in 
Rana under the name of Dilatator laryngis'), named here according 
to its function, but its homology with the dorso-laryngeus of Urodeles 
seems to be clearly proven, not merely by the comparison of adult 
forms, but also by the investigation of frog tadpoles where the relation 
of parts is almost identical with that of Triton. 
d) Phylogenesis of the laryngeal muscles. 
This question naturally resolves itself into two problems, regard- 
1) WIEDERSHEIM, Lehrbuch d. vergl. Anat. S. 628. — EckER u. 
WIEDERSHEIM, Anat. d. Frosches, 3. Abteilung, S. 30. 
LT a ——— 
