22 INTRODUCTION 



f oraminifers, and the pyramids of Egypt are built of nummulites, 

 another genus of Foraminifera. It is estimated that an ounce 

 of this deposit contains four millions of these protozoans, so it is 

 impossible to conceive the numbers of once living animals repre- 

 sented in the tombs of the Pharaohs. Telegraph-cables raised 

 from the depth of two miles bring the message to naturalists 

 that the bottom of the ocean at that depth is composed of little 

 else than the calcareous shells of Foraminifera. 



Many of the lower animals resemble plants in form. Hydroids 

 and polyzoans are often gathered and preserved as seaweeds. 

 Corals, sea-anemones, and holothurians are curiously like plants. 

 For a time the confusion about the division of animals and plants 

 was partly owing to this resemblance of forms, and the theory 

 of the animal nature of corals was for a long time considered to 

 be refuted by the testimony of a naturalist who declared that he 

 had seen them in bloom. Later this class of animals was 

 believed to occupy an intermediate sphere and partake of the 

 characteristics of both kingdoms. The name zoophyte, meaning 

 " animal-plant" or " mingled life," was adopted because of these 

 resemblances and was formerly applied to these forms only. 

 To-day it has a broader application. There is still a neutral class, 

 called Protista, comprising organisms which have not yet been 

 classified as plants or animals. 



