1348 THE STORY OF THE UNIVERSE 



by the delicate processes, each consisting in reality 

 of a network of blood-vessels, in which the blood is 

 exposed to the oxygen of the water, and is thus puri- 

 fied. In the sea-horses, however, the gills do not 

 present this comb-like appearance, but exist in the 

 form of separated tufts or bunches of delicate fila- 

 ments, which spring from the gill-supports or arches. 

 From this peculiarity the name "tuft-gilled," already 

 alluded to, is derived, and the pipe-fishes agree in 

 the structure of the gills with the sea-horses. Then, 

 also, as most readers are aware, the gills of ordinary 

 fishes are covered by a horny plate, appropriately 

 named the gill-cover, and it is by sharply compressing 

 the gills with this cover that the water used in breath- 

 ing is ejected from the gills, so as to make room for 

 a fresh supply. In the sea-horses, however, the gill- 

 cover is not open or free at its under and hinder 

 edges, but is firmly attached all round to the neigh- 

 boring tissues, and so rendered immovable. At one 

 point in its circumference, however, a small aper- 

 ture is left, through which the breathing-water 

 escapes from the gills. 



The sea-horses are found abundantly in the English 

 Channel, around the coasts of France and Spain, in 

 the Mediterranean Sea, and in the tropical oceans. 

 Several distinct species are known to zoologists, but 

 they closely resemble one another in the essential 

 features just noted. They are lively and intelligent 

 little creatures, and become familiar in time with 

 their possessors. Fixed by their tails, they may be 

 seen actively to dart the head at any passing object 

 adapted for food ; while, when they wish to free their 



