Chapter 14 

 PROTOZOA 



The Protozoa are minute animals, for the study of which 

 it is necessary to use a compound microscope. They are there- 

 fore hardly to be classed among the "common objects of the 

 country side," at least from the standpoint of the casual observer. 

 Yet it is interesting to contemplate a shady pool, or a mossy 

 swamp, and realize that such places support a population of 

 millions of minute creatures, which live, work, feed and reproduce, 

 but do not necessarily die. They may die through accidents, 

 we may swallow some of them in our drinking water; but there 

 is no obligatory death, since reproduction is by division into two 

 or more individuals. The two children are not merely derived 

 from the parent, they are the parent, all of it, now consisting of 

 two persons instead of one. We speak of the Protozoa as con- 

 sisting of one cell, or vital unit, instead of millions as the case 

 with ourselves. They are unicellular, we are multicellular. We 

 also think of them as very primitive, and comparatively very 

 simple. They are not, in fact, so simple as we might believe; 

 some of them are very extraordinarily complex for such micro- 

 scopical objects. Careful study reveals many remarkable 

 features, and shows us that there are almost innumerable genera 

 and species, differing by quite recognizable characters. In spite 

 of all this diversity, there is a tendency to conservatism, which has 

 kept many of the species practically unchanged for very long 

 periods. How do we know this? Because when we investigate 

 the freshwater Protozoa of remote countries, lakes in temperate 

 regions, tropical islands, antarctic shores, the same species turn 

 up over and over again. It must have taken immense periods 

 for these little animals, originating somewhere on the earth, to 

 spread so widely. Were they more plastic, more easily in- 

 fluenced by conditions, we might expect to see entirely different 

 forms in diverse countries and climates, as is generally the case 

 with the higher animals. Clathrulina elegans, having a spherical 

 yellowish or brown shell on a stalk, was discovered at the city 

 now called Leningrad, but we obtained it near Ward, in Colorado. 

 Dr. Eugene Penard, the well-known Swiss authority on Protozoa, 

 once visited Colorado, and collected in Boulder County a new 



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