156 THE THEORY OF EVOLUTION 



itary modifications in several of them, of which a 

 few may be mentioned here. A salamander, black 

 with yellow spots, which lives in damp woods, is 

 viviparous and produces sixty to seventy gill-bearing 

 larvae, which are deposited in water and develop 

 there for several months, leaving the water for the 

 land at the time of metamorphosis, when the larvae 

 become adult, air-breathing salamanders. If captive 

 animals are deprived of water in which to deposit 

 their young, a very few are produced, but these are 

 not larvae, but little salamanders like their parents. 

 When this second generation breeds, if it is allowed 

 access to water, it will once more produce larvae, but 

 very large ones, which leave the water in a few days, 

 instead of remaining in it for several months. If 

 adult salamanders of this species are kept for years 

 on yellow soil, the yellow spots and blotches greatly 

 enlarge, encroaching on the black ground, and the 

 effects of this treatment are much increased in the 

 second generation, showing a cumulative action. 

 The larvae of a toad were, by means of darkness, 

 cold water, and other unnatural conditions, made to 

 delay their metamorphosis and became sexually ma- 

 ture and able to breed while in the tadpole stage. 

 These tadpoles attained great size and their offspring 

 did not advance beyond the stage in which the hind- 

 legs are developed, remaining in that condition for 

 years and showing no tendency to metamorphosis. 

 Other experimenters have failed to repeat these re- 

 sults, which are strongly questioned. 



