THE FRESH WATERS 159 



fend for itself. Indeed, the young crayfishes 

 that have begun to swim about often seek the 

 shelter of the mother's tail, as chickens the hen's 

 wings. This shortening down of the chapters 

 of the life-history is an adaptation that tends 

 to circumvent some of the dangers of youth. 

 The time taken to grow up may vary even 

 among the same animals according to the sea- 

 son, and may be very different in two closely 

 related species. There occurs throughout Cen- 

 tral Europe a larger cousin of our common 

 newt, known as the "fire-salamander," from 

 the large splashes of orange colour on its black 

 body. It brings forth its young alive, but still 

 surrounded by the egg envelope, which bursts 

 at once, setting free a gill-bearing tadpole. 

 This little creature does not take on the sala- 

 mander form, or leave the water until it is 

 about three and a half months old. But if the 

 summer is dry, and the water in the pools gets 

 low, the stages are gone through more rap- 

 idly, and development may be complete at the 

 end of two months. This salamander is not 

 found at a greater height than 2500 feet. 

 Above that its place is taken by another very 

 similar form without the orange spots, known 

 as the black salamander. This form may 



