Corals, Worms, etc. 



comes in contact with water, the shell is thrown off and 

 the amoeba resumes its normal life. 



A little higher up the scale of development we find 

 creatures almost as minute as the amoeba, which, however, 

 are covered with solid armour as beautiful as it is varied. 

 These little creatures, called foraminifera, float freely in 

 the waters of the ocean and when they die their shells sink 

 to the bottom. As there are countless millions of these 

 creatures in certain parts of the ocean, their shelly deposits 

 are of considerable extent and, in course of time, after 

 long ages, in fact, the pressure of the water welds them 

 together and they form chalk. Heat, in addition to 

 pressure, which occurs when volcanic action occurs in 

 the deposits of foraminifera, results in the formation of 

 marble. Many of these lowly animals are quite unable to 

 exist as individuals, they therefore combine together to 

 form colonies, where each being sinks its own individuality 

 for the good of the colony. 



Sponges, which are almost plant-like in growth, are 

 merely colonies of minute animals. "They are living 

 thickets in which many small animals play hide-and- 

 seek." Their most striking peculiarity, from our point of 

 view, is the fact that they form so-called spicules of silica. 

 Silica is the substance of which flint is composed, and the 

 sponge spicules are of real beauty, needle-shaped, star- 

 shaped, dumbbell-shaped, like studded clubs, and a hundred s 

 and one other forms may be found ; in fact, they make 

 beautiful objects for the microscope. To the sponges 

 they act as some protection against their enemies. More 

 remarkable than the beautiful shapes of the spicules is the 

 power possessed by the sponges of extracting the silica 

 for their manufacture from the sea-water in which they 

 dwell. Sea-water is said to contain about one and a half 

 parts of silica to a hundred thousand parts of water ; there- 

 fore, to form an ounce of spicules a ton of sea-water must 

 pass through the body of a sponge. 



Very closely related to the sea-anemones of our coasts 



288 



