AMPHIBIA. 



117 



The other types of Myctodera, so far investigated, agree fairly with the 

 Newt. 



The larva of Amblystoma punctatum (fig. 84) is provided with two 

 very long processes {s), like the suctorial processes in Triton, placed on the 

 throat in front of the external gills. They are used to support the larva 

 when it sinks to the bottom, and have been called by Clark (No. 98) 

 balancers. On the development 

 of the limbs, these processes drop 

 off. The external gills atroj)hy 

 about one hundred days after 

 hatching. 



It might have been anticipated 

 that the Axolotl, being a larval 

 form of Amblystoma, would agree 

 in development with Amblystoma 

 punctatum. The conspicuous suc- 

 torial processes of the latter form 

 are however represented by the 

 merest rudiments in the Axolotl. 



The young of Salamandra 

 maculata leave the uterus with 

 external gills, but those of the 

 Alpine Salamander (Salamandra 

 atra) are born in the fully de- 

 veloped condition without gills. 

 In the uterus they pass through 

 a metamorphosis, and are provided 

 (in accordance with the principle 

 already laid down) with very long 

 gill-filaments '. 



Salamandra atra has only two 

 embryos, but there are originally 

 a larger number of eggs (Von Sie- 

 bold), of which all but two fail to 

 develop, while their remains are 

 used as pabulum by the two which 

 survive. Both species of Sala- 

 mander have a sufficient quantity 

 of food-yolk to give rise to a yolk-sack. 



Spelerpes only develops three post-hyoid arches, between which slits are 

 formed as in ordinary types. Menobranchus and Proteus agree with 

 Spelerpes in the number of post-hyoid arches. 



One of the most remarkable recent discoveries with reference to the 

 metamorphosis of the Urodela was made by Dumerill He found that 

 some of the larvae of the Axolotl, bred in the Jardin des Plantes, left the 

 water, and in the course of about a fortnight underwent a similar meta- 

 morphosis to that of the Newt, and became converted into a form agreeing 

 in every particular with the American genus Amblystoma. During this 



1 Allen Thomson informs me that the crested Newt, Triton cristatus, is in rare 

 instances viviparous. 



2 Comptes Rendtis, 1870, p. 782. 



Fig. 84. Labv^e of Amblystoma puncta- 

 tum. (After Clark.) 



n. nasal pit; /. oral invagination; op. 

 eye; s. balancers; f.l. front limb; br. bran- 

 chiae. 



