34o LAKES AND STREAMS 



with its mouth, and by violent shaking of its head gradually pulls out of 

 their shells. 



While newts require a great deal of food during their sojourn in the water, at 

 which time they even eat their own skins when just stripped off, their appetites 

 are small when on shore, where they feed principally on worms and slugs. Their 

 movements are lively and graceful only in the water. There thej r swim quickly 

 about with their tails, rising straight up to the surface to breathe, and then sinking 

 in curves to the bottom, where they often snap their mouths and emit bubbles 

 of air. On land they are much slower and clumsier. Like salamanders, they 

 emit a fluid from the glands of the skin, which, if not exactly acrid and poisonous, 

 is offensive to many animals, though useful to the newts themselves, owing to its 

 stickiness. By means of this fluid they are enabled, not only to adhere to, but to 

 climb glass and other vertical planes. Much as newts enjoy living in water during 

 the spring, they by no means like it later on, when the}- show their aversion to 

 an involuntaiy bath by sprawling violently with their feet, and lifting and turning 

 their heads, and trying to escape as soon as possible. Indeed, if they do not 

 succeed they are drowned. Early in the nineteenth century certain observations 

 were published about the voice of these newts, which shewed that the crested 

 as well as the common species utters a loud squeak. The voice of the Alpine 

 newt was discovered to be a flute-like sound as char as a bell, and both 

 male and female of the common newt are also known to have a cry. Whether 

 newts are really so very long-lived as has been asserted, may be doubtful, but 

 they an' distinguished from all other vertebrates by the facility with which they 

 reproduce any parts they may lose. Though many statements of their repro- 

 ductive powers may be exaggerated, it is certain that they are able to replace not 

 only their legs but even their eyes. 



Before referring- to the species characteristic of the fresh waters 



Perch etc. 



of Europe, a few words are desirable with regard to the structure of 

 fishes, which form one of the lowest class (Pisces) of vertebrates, but, owing to the 

 plan of the present work, the notice is brief. Most of the fishes of the pi'esent day 

 are clothed with overlapping scales, although a few are naked ; some are protected 

 by separate rows of bony shields, and yet others by a complete suit of armour, 

 while others, again, especially in the tropics, have gorgeously coloured skins 

 beneath the scales. The majority, however, display less vivid colours, which change 

 according to age, sex. and season, and disappear soon after death. The reason 

 of this is that within the skin there lie small pigment-cells mostly filled with 

 black, but sometimes with red or yellowish colouring matter; these cells being 

 capable of sudden contraction by which they are so reduced in size as to be 

 almost invisible, while, on the other hand, they are also capable of sudden 

 expansion into star-shaped bodies, which show the colour to the best advantage. 

 By this means a fish is enabled to accommodate its hue to that of its sur- 

 roundings; and as this change of colour is absent in blind species, it evidently 

 depends on the degree to which the species is sensitive to light. In the skin of 

 many species, especially those of the carp family, there are spots where the 

 black cells are entirely or partly wanting, and the red ones are strongly 



