l6o ZOOLOGY 



A naturalist of Holland, Leeuwenhoek, first discovered the 

 Infusoria, and thus opened up one of the most interesting 

 departments of zoology. It was not until the middle of the 

 nineteenth century that the simple, unicellular structure of 

 the Protozoa was really understood. Many of them can endure 

 drying, be blown about in the spore stage, and then take up 

 active life again on the return of water, so that thereupon, in a 

 few hours, Infusoria may literally swarm where none seemed to 



FIG. 74. A compound Foraminiferan Nodosaria. a, aperture of shell; /, food particles 

 captured by the strands of protoplasm outside the shell; n, nucleus; sh, shell. 1-4, the successive 

 chambers of the shell; i, being the oldest. 



Questions on the figure. Does this seem a colony or a single individual? 

 Why ? Why is digestion possible outside the capsule ? Compare this with figures 

 of Protozoa in which there is no large aperture to the shell. 



be. This is responsible for the long life of the old belief that 

 they arose by "spontaneous generation," that is, without 

 parents. It is only in recent years that this belief has been 

 finally disproved. It is known that they do not appear in 

 water that has been boiled and kept free from exposure to the 

 air. Much brilliant work has been done on the group in recent 

 years, on structure, on behavior, and on their relation to disease. 



201. Classification of Protozoa. The following are the principal classes of 

 Protozoa. 



