Z42 CHAPTERS ON EVOLUTION. 



other parts of the animal or even of the vegetable kingdom. Just 

 as in language long compound words have a tendency to concision, 

 and single letters sometimes linger on, indicating the history of a. 

 word, like the ' 1 ' in ' alms/ or the ' b ' in ' debt/ long after they 

 have ceased to influence the sound ; so in embryology useless stages, 

 interesting as illustrations of past history, but without direct advan- 

 tage under present conditions, are rapidly passed through, and even, 

 as it would appear, in some cases altogether omitted." 



We may here refer to the case of the Mexican Axolotl (Fig. 160), 

 on account of its peculiar development, and also from its bearings 

 on that of another member of the frog's class the black salamander 

 (Salamandra atrd] of the Alps and its curiously modified life-history. 

 The Axolotl is a Mexican eft or newt, which retains the gills of early 

 life along ^with the lungs of the adult stage. It breeds freely in 

 captivity, and hence was long regarded as a mature and adult animal. 

 But in 1867 some axolotls were observed to emerge from the water in 

 the Jardin des Plantes at Paris, to cast their skins, and to become 

 transformed into a gill-less newt long known as an American genus, 



FIG. 163. AMBLYSTOMA. 



and named Amblystoma (Fig. 163). Such a change was almost 

 equivalent to that whereby a frog could be metamorphosed into a 

 toad, and hence it excited no small surprise in the zoological world. 

 By careful experimentation a lady naturalist, Fraulein von Chauvin, 

 showed that by gradually inuring the Axolotl first to a life amongst 

 damp moss, and then to an existence entirely removed from the 

 water, it could be made to assume the Amblystoma-form, with its 

 black skin and yellow spots. Weismann states that the transfor- 

 mation occupies fourteen days, and Dumeril states the period of 

 metamorphosis as sixteen days. 



Fraulein von Chauvin states, in her account of the Axolotl's meta- 



