174 NATURE STUDY IN SCHOOLS. 



The shell covered amoebae, with at least as complicated a structure, and 

 considerable more intelligence, carefully select material with which to build 

 up their domiciles. Propagation is by division. This form certainly possess- 

 es a circulatory organ. Locomotion is accomplished by pseudopodia. 



In the slipper infusoria we find locomotive organs present in the form 

 of cilia by the aid of which the animals move rapidly through the water. 

 Here we also find the first evidence of the interchange of a fertilizing ele- 

 ment. Propagation by division. On account of the exigencies of a wandering 

 life, more intelligence is required to avoid accidents and to maintain the specie s 

 intact. 



In the bell infusoria we see a slight retrogression in the fact that the an- 

 imal is attached by a stem to a base. But on account of the length and 

 fbxibitity of this stem, the aiimal enjoys a considerable degree of freedom* 

 while by its direct aet of fertilization, it establishes an advance in the method 

 of propagation over most of the other protozoa. 



As a summary of advancemant in protozoa, we have physically ; first, 

 the skillful construction of an outer covering; second, the appearance of ru- 

 dimentary muscular action ; third, locomotion, slow, by pseudopodia and more 

 rapid, by cilia and flagella ; fourth, circulation by a contracting vessicle : fifth, 

 fertilization by conjugation, as in the slipper infusoria, and direct as in the 

 bell infusoria; mentally, intelligence displayed in the construction of an in. 

 tricate outer covering of acquired material, and in the avoidance of accidents 

 in rapid motion. 



Collecting and Preserving Specimens of Protozoa. 



Although most of the species of this group are so small that a microscope 

 is required for theii study, nd for this reason they must be mounted upon 

 glass slides, a few can be seen with the unaided eye or with a common mag- 

 nifying glass. In order to mount objects as small as are the greater number 

 of species of protozoa, considerable skill and experience is required, but the 

 larger forms of foraminifera, such as the Orbitulina adunca, found in the 

 sands of beaches and shallow water, ( see fig. 55 ) and the red species, found 

 beneath coral, both from the Bahama Islands, can be kept in vials. 



Other species of Protozoa occur in the ooze of mud of fresh and salt 

 water, damp moss, damp earth, and clinging to water plants, submerged 

 sticks, stones, etc. 



