146 DARWINISM AND THE PROBLEMS OF LIFE 



rays of the sun. When it is very cold, the outflow of 

 gas ceases, and the spawn sinks to the bottom of the 

 water, and is protected there from the wind and frost. 



The wonderful contrivances of the frog-spawn show 

 that all the stages of the animal's career are subject to 

 natural selection. Only those animals have a prospect 

 of transmitting their character to the next generation 

 which lay eggs that will escape the eye of the enemy 

 and the injury of bad weather. Whole pages might be 

 written on the adaptations of the eggs in the early 

 stages of the animals, and we shall see more about 

 them later on. 



We must not leave the amphibians without drawing 

 attention to one of their best adaptations. This is the 

 character of their skin. It is not merely that this 

 represents the chief breathing-organ in this class, and 

 so enables a lungless frog to survive longer ; it also 

 affords the greatest protection to the animal. The 

 secretion of the cutaneous glands of the amphibians 

 is well known, and a good many legends have been 

 told of the salamander, which has been credited with 

 the power of remaining unhurt in fire. There is this 

 much truth in them, that the animal can remain for 

 some time over a gentle fire, as its glands give out 

 their secretion more freely under heat. But the pur- 

 pose of this juice is to disgust the enemies of the frog. 

 This is chiefly attained by the offensive smell, but 

 also by the corrosive nature of the fluid. The toad- 

 secretion is not poisonous for human beings, though 

 it causes inflammation if it touches the eyes, but it 

 may be fatal to small animals. 



