THE SEA. 



shells, as a rule, nearly invisible to the naked eye, and enclosing-, or once having- enclosed, a 

 living- organism. The sand of the sea-shore is often one-half composed of them. M. 

 d'Orbig-ny found in three grammes (forty-six grains troy) of sand from the Antilles no less 

 than 440,000 of these minute shells. Ehrenberg, the German microscopist, was once 

 invited by the Prussian Government to assist in tracing the robbery of a special case of 

 wine. It had been packed in sand only found in an ancient sea-board of Germany, and from 

 this fact and knowledge of locality the thief was detected. The Foraminifera, small as they 

 are, have helped to form enormous deposits, obstruct navigation in g-ulfs and straits, and 

 fill up ports, as may be seen at Alexandria. In various geological strata they are found ; they 



exist in immense quantities 

 in the chalk cliffs of this 

 country. In the Paris chalk 

 their remains are so abundant 

 that a block of little more 

 than a cubic yard has been 

 computed to contain three 

 thousand millions! "As/' 

 says Figuier, "the chalk 

 from these quarries has served 

 to build Paris, as well as the 

 towns and villages of the 

 surrounding departments, it 

 may be said that Paris, 

 and other great centres of 

 population which adjoin it, 

 are built with the shells of 

 these microscopic animals." 



The Infusoria almost 

 baffle the attempts of na- 

 turalists to classify them, 



while their very existence would have escaped us but for the discovery of the microscope, 

 "the sixth sense of man/' as Michelet happily termed it. In the tropics, water collected 

 at a great depth was found to contain 116 species; in the Antarctic regions the very ice 

 was found to contain nearly fifty different species. The very largest kinds can hardly be 

 seen by the naked eye. They are generally nearly colourless, but some of them are never- 

 theless green, blue, red, brown, and even blackish. Some of those most commonly noted, 

 on account of their superior size, are furnished with hairy cilia, which act as paddles, while 

 certain of them appear to be employed in conveying food to the mouth. 



The Infusoria reproduce their species in several ways : by a kind of budding, 

 like plants, by sexual reproduction, and by fission i.e., the spontaneous division of 

 the animal into two parts. " By this mode of propagation," says Dujardin, " an Infusorian 

 is the half of the one which preceded it, the fourth of the parent of that, the 

 eighth of its grandparent, and so on." The process is represented in the accompanying- 



FORAMINIFERA IX A PIECE OF ROCK. 



