46 AMPHIBIA 



CHAT. 



The same kind of organs occur in Ainhlystoinn} They appear, 

 previous to the breaking open of the gill-clefts, as protrusions of 

 epiblast, long before any of the external gills on the branchial 

 arches. When the clefts have broken open, the quadrate sends 

 out laterally a tiny crescent-shaped process a little above the jaw- 

 joint, and this process extends to the base of the Ijalancer, but 

 not into it, and a bundle of muscle-cells grows into tlie balancer. 

 It is easy to recognise the same organ in the extremely long 

 thread-like structures of the larva of Xetiopiis. In the Apoda 

 they are likewise present, but are retained permanently as highly 

 specialised, probably tentacular organs (cf. p. 86, A]ioda^;. 



One of the most unexpected features is the suppression of 

 the lungs in various kinds of Salamandridae. The lungs are 

 either reduced to useless vestiges or they are quite absent. This 

 occurs in aquatic and terrestrial, American aud European forms, 

 and it is noteworthy that the reduction of the lungs does not 

 apply to all the species of the various genera, nor is it restricted 

 to one sub-family. 



The followinu' list is due to the researches of H. H. AVilder,- 

 L. Camerano,'^ E. Lonnberg,'^ and G. S. Hopkins ^ : — All the 

 Desmognathinae and Plethodoutinae ; Amblystomatiuae, Amhly- 

 stoma opacum ; Salamandrinae, Salamandrina perspiciUata. In 

 Triton and other Salamandrinae the length of the lungs varies; 

 in some they extend more, in others less, than half way down the 

 distance between head and pelvis. Hopkins remarks : " Two 

 questions are naturally suggested by this apparently al)erraut 

 condition of the respiratory organs. First, what structures or 

 orLmns have taken on the function of tlie lunys and l)ranchiae ; 

 and secondly, is there any modification in the form or structure 

 of the heart which in any way may be correlated with the abo^•e- 

 mentioned jjeculiarities of the lungless forms?" Wilder con- 

 cluded that respiration was probably carried on by the skin, and 

 perhaps, to some extent, by the mucosa of the intestine. Cameranij 

 thinks that, at least in the European forms, respiration is effected 

 by the bucco -pharyngeal cavity, and that the skin affords no 

 efficient aid. The left aimcle in tlic lungless forms is much 



' Orr, Quart. J. Micr. Set. xxix. 1889, p. 316. 



- "Luiigenlo.se Salamandridrn," JnM. Anz. 1894, p. 676 ; 1896; i-. 1^. 

 •' " Xuovu licerclie aiiatoiiio-tisiologiclie intoriio ai Saluniandridi nonualmeiite 

 apneuiuoui." Torino, 1S91. 



•* Zvol. An:. 1896, p. ■'/■'> ; 1899, p. rjl.'). •■■' Amcr. Xalaral, xxx. 1886, p. .^29. 



