170 SYSTEMATIC ZOOLOGY FOR TEACHERS. 



But I, Nature's child on Life's Ocean, 



A wanderer on that vast sea, 

 Knowing not where my bark may be stranded 



Can sympathize with thee. 



Cayman Brac, April 6, 1888. 



SYSTEMATIC ZOOLOGY FOR TEACHERS. 



BY 



C. J. Maynakd. 



( continued. ) 

 Protozoa ; General Conclusions. 



Minute and inconsequental as, the organisms known as Protozoa at first 

 sight appear, we have seen that they are really of great importance to man. 

 To them we owe much of the limestone of the world. Many of the species 

 are scavengers, devouring bacteria, which, if not kept in check by this means, 

 would prove very injurious to man. 



From an evolutionist's standpoint, the study of this lowly group of ani- 

 mals is exceedingly interesting and instructive. With these, or similar or- 

 ganisms, which lived in the ages past, life began. In fact, today all life, 

 from man down to the lowest fuim of animal existence, begins with the sin- 

 gle cell. 



From the single celled animal then all animal life has been derived. Frcm 

 this simple beginning, we can trace all gradations in the mechanisms of an- 

 imal life up to the complicated structures found in man. From the single celled 

 animal we can, in much the same way, trace all giadations in mind up to 

 the intellect of the most intelligent man living. For undoubtedly with these 

 minute organisms mind began. Let him who is not inclined to believe this, 

 watch the movements of an amoeba for a time. See it flow smoothly through 

 the water in any direction it chooses to go. Most assuredly these movements 

 are made at will, are performed in response to some inner impulse, in answer 

 to the commands of some mind, rudimentary and imperfect though it be. 

 Let those who would deny that the amoebae have a mind, study with care 

 the structure of the shells of some of the species. These are made of minute 

 sand grains. ( See fig. 77). Note with what care each of the varying grains 

 is selected in order to fit the interstices formed by other grains. Angular 



