The Microscope, 305 



of this group, in which the tentacles become marvelously flexible; 

 this is notably the case in Ephelotida and in Podophyra flexilis, a 

 fresh water species described by myself in The Microscope for 

 August, 1887. In this form the long, extensible and constantly 

 writhing arms remind one of a veritable octopus. 



Another equally instructive series is that of the manner of 

 and contrivances for food ingestion. In the simplest forms this 

 takes place by simply engulfing it; a little higher in the series it is 

 received through the body walls at restricted areas; then a well- 

 defined and guarded aperture is found, often reinforced by a won- 

 derfully complex system of chitinous or otherwise indurated 

 appendages, or it may consist of sucking tubes, sometimes flexible. 

 But enough of these details, which have been enumerated not only 

 to show the mutual relatives of the groups which result from the 

 fact of descent from common ancestors, but to present certain terms 

 by which to make easy the explanation of the persistency of 

 protozoic functions in the associated cells of the tissues of multi- 

 cellular animals; thus the amoeboid motion of the colorless blood- 

 corpuscles and other cells, the contractions of the muscle cells, the 

 cilia of the epithelium of the trachea and ventricles of the brain 

 are examples. 



The protozoa, lowly as they are in organization and insignifi- 

 cant in size, have from the dawn of animal life on the ' earth to the 

 present, played a leading part ' in the great problems and progress 

 of the world. Biological evidence is irresistible in proof that the 

 first manifestation of animal life was protozoic; that the capabilities 

 of development on this type were finally exhausted, and that there 

 radiated from the protozoic line at different stages, certain metozoic 

 types. All through the ages of change they have kept persistently 

 to their work. The heat and drouth of siimmer or the frosts of 

 winter cannot destroy them; when the water of the transient 

 streams disappears or food fails, they simply wrap about their frail 

 bodies an impervious mantle, to retain their own moisture, and fall 

 asleep until returning favorable conditions restore them to activity; 

 then again the battle of life goes fiercely on beneath the surface. 

 Each feeds ravenously upon unicellular plants or mercilessly on 

 those of its kind smaller than itself, and, in turn, is destined to be 

 swallowed by one that is larger. Notwithstanding this inevitable 

 destruction, their prodigious powers of multiplication and repro- 

 duction ever maintain them against the vicissitudes of climate or 

 the distress from enemies. This invisible link, uniting the animal 



