170 ANIMAL BIOLOGY 



anguinus which lives in dark caves in Austria. Like 

 many other cave animals it has become entirely blind and 

 the body has lost nearly all of its pigment. 



Most of the higher tailed amphibians, such as the 

 tritons, newts and salamanders, do not have gills in the 

 adult state, although gills are usually present in the young. 

 Some species live in the water and some on the land. 

 Of the land forms the European spotted salamander is 

 remarkable for its conspicuous colors. The skin of this 

 animal secretes a very poisonous, milky fluid which affords 

 it a sufficient protection, since most animals which live in 

 the same region know that the spotted salamander is some- 

 thing to be left alone. Its conspicuous colors are supposed 

 to be of value in enabling it to be easily recognized and 

 therefore in preventing it from being molested. Such 

 colors are commonly called " warning colors" and they are 

 not infrequent in animals which are poisonous or distasteful. 

 Some of the Urodeles, such as Triton, can regenerate 

 missing legs or tail, or even the eye, but in the frogs and 

 toads this power is very limited. 



The tailless amphibians, or Anura, comprise the most 

 highly developed amphibians. They are generally found 

 on the land, but in most cases they lay their eggs in the 

 water and the young hatch as tadpoles which resemble 

 the most primitive urodeles in having external gills and 

 well-developed tails. The series of forms which we meet 

 in passing from the lowest to the highest Amphibia is 

 roughly similar to the stages passed through in the devel- 

 opment of an individual frog or toad. 



The breeding season of frogs and toads is in the spring 

 when the animals repair to the water to deposit their 

 eggs. The eggs laid are surrounded by a transparent 

 jelly which affords them a certain protection. During the 

 breeding season the females are clasped by the males which 



