THE EVOLUTION THEORY 



121 



the embryos at this stage from the oviduct, and place them into 

 water we shall observe that in spite of the abnormal conditions 

 the gills are still able to discharge their proper functions. Here 

 it is clear that the black salamander descended from ancestors 

 whose larvae were aquatic and breathed through gills, and that 

 the habit to bear the young up to the complete development can 

 only be a recently acquired character. 



FIG. 33. Ambly&toma tigrinum. 



On the land, the adult form ; in the water, the larval form, Axolotl, formerly 

 called Siredon axolotl or S. pisciformis. 



An opposite instance is furnished by the well-known Mexican 

 Axolotl, for it is able, under ordinary circumstances, to pass its 

 entire life and to reach maturity and power of reproduction in 

 the gill-breathing larval stage. Formerly it was even thought 

 that the larval form was its permanent form, and it was conse- 



