296 THE SALAMANDER 



addition a M. opercularis joining the operculum to the shoulder, 

 whereas in almost all higher forms either one or other alone is present. 

 The 'hearing' of Urodeles must obviously be confined to the per- 

 ception of a very small range of low-frequency vibrations of wide 

 amplitude, but it is possible that the M. opercularis may have the 

 effect of increasing the range somewhat, since, being a striped muscle, 

 its tension is capable of adjustment by the animal. 



3. The Membranous Labyrinth (PI. XXIV, figs. 80 and 81). 



Apart from the earlier workers (e.g. Scarpa, Pohl, Huschke, Win- 

 dischmann, &c.) the first investigator to make a really detailed study 

 of the membranous labyrinth of Amphibia was Hasse (1873). He 

 was succeeded by Kuhn (1880), whose paper was, in turn, closely 

 followed in the next year (i 88 i) by the well-known work of Retzius. 

 All these authors give excellent descriptions of the ear of Salamandra 

 and are, in the main, correct. They all fall into the same error in 

 imagining that the ductus perilymphaticus communicates with the epi- 

 cerebral space — a mistake which was corrected later by O'Neill, 

 Sterzi, Harrison, &c. Both Hasse and Kuhn imagined that t\\G.pars 

 neglecta (their /)<2rj tnitialis) was the anlage of the cochlea of mammals, 

 but Retzius did not share this view, and to him is due the name -pars 

 neglecta. Both the earlier authors describe a pars hasilaris supported 

 by a 'cartilaginous' frame (Knorpelrahmen). Retzius denies the exis- 

 tence of both a pars hasilaris and a 'Knorpelrahmen'. In this, how- 

 ever, he is himself in error (as Harrison (1902) showed), and the 

 earlier authors were right. Both Kuhn and Retzius deal with the 

 microscopic structure of the maculae, &c. 



The membranous labyrinth of Salamandra is fairly typical of Uro- 

 deles in general, but differs in several points from that found in 

 Anura, e.g. the Frog. After clearing away the muscles arising from 

 the auditory capsule the ridges over the semicircular canals may be 

 clearly seen. In order to remove the labyrinth from the capsule — 

 not a particularly difficult operation — it is advisable to decalcify the 

 skull by immersing it in sulphurous acid. The roof of the capsule may 

 then easily be cut away. Care must be taken with the anterior septum 

 semicirculare (a bony pillar joining the roof to the ventro-mesial wall 

 of the capsule), which lies just posterior to the anterior semicircular 

 canal, and serves to separate this canal from the main cavity. The 

 other two septa, related in the same way to the other semicircular 

 canals, are rarely complete, so they do not usually give trouble. 



Compared with the size of the skull as a whole the ear is large and 

 flat, and, in most places, is well separated from the bony capsule. 



