SURFACE-SWIMMING FAUNA (VERTEBRATES). 125 



spawn in the open sea, five or ten miles from the 

 coast, during the spring time. The egg of the 

 Mackerel, unlike that of the Herring, 3oes not 

 sink to the bottom when it is spawned, but, being 

 provided with a large oil globule, it is light 

 enough to remain on the surface until the young 

 larva is hatched. After the spawning has taken 

 place the Mackerel approach the coast, and will 

 even enter bays and narrow inlets on the shores 

 in pursuit of the young Sprats and other small 

 Fish upon which they prey. 



A great deal could be written on the history 

 of the Pilchards, the Anchovies, the Sprats, and 

 other Fish which frequent the surface waters of 

 the sea in the neighbourhood of the European 

 coasts. No two species seem to have pre- 

 cisely the same habits, and what is known 

 about them presents us with many curious 

 and remarkably interesting facts. For further 

 details, however, I must refer the reader 

 to the larger and more comprehensive books 

 dealing specially with the subject, for space 

 must still be found for a few words on another 

 group of animals which play a conspicuous part 

 in the story of life in the seas. 

 * The animals composing the class of Mammals 

 are distinguished from other Vertebrates by the 

 fact that the females are capable of providing 

 milk for their young ones after birth. Most of the 

 Mammals are strictly terrestrial, but three orders, 

 namely, the Cetacea, the Sirenia, and the Carnivora 

 contribute to the surface-swimming population of 

 the sea. 



The Cetacea are all aquatic. The order in- 



