12 HANDBOOK OF PROTOZOOLOGY 



the soil by the nitrifying bacteria, several investigators have 

 brought out the fact that in the soils of temperate climates 

 Protozoa are present and active throughout the year. The exact 

 relation between specific protozoans and bacteria in the soil is 

 a matter which still awaits future investigations, although 

 numerous experiments and observations have already been 

 made. All soil investigators should be acquainted with the 

 biology and taxonomy of free-living Protozoa. 



It is a matter of common knowledge that the silkworm and 

 the honey bee suffer from protozoan infection known as micro- 

 sporidiosis. Sericulture in southern Europe suffered great dam- 

 ages in the middle of the nineteenth century because of the 

 "pebrine" disease caused by the microsporidian, Nosetna bom- 

 hycis. During the first decade of the present century, another 

 microsporidian, Nosema apis, was found to destroy occasionally 

 a large number of honey bees. Methods of control have been 

 developed and put into practice so that these microsporidian 

 infections are at present not serious, even though they still 

 occur. On the other hand, other Microsporidia are now known 

 to infect certain insects, such as mosquitoes and lepidopterous 

 pests, which, when heavily infected, die sooner or later. 

 Methods of artificial destruction of these insects by means of 

 chemicals are more and more used, but attention should be 

 given to ultilization of the parasitic Protozoa and Protophyta 

 for this purpose. 



While the majority of Protozoa lack permanent skeletal 

 structures and their fossil forms are unknown, there are two 

 large groups in the Sarcodina which possess conspicuous shells 

 and which are found as fossils. They are Foraminifera and 

 Radiolaria. From early Palaeozoic times down to the present 

 day, the carbonate of lime which makes up the skeletons of 

 Foraminifera has been left embedded in various rock-strata. 

 Although there is no distinctive foraminiferan fauna character- 

 istic of a given geologic period, there are certain peculiarities of 

 fossil Foraminifera which distinguish one formation from the 

 other. From this fact one can understand that knowledge of 

 foraminiferous rocks is highly useful in checking up logs in well 

 drilling. The skeletons of the Radiolaria are the main con- 

 stituent of the ooze of littoral and deep-sea regions. They have 



