APPENDIX TO PART II 



CLASSIFICATION OF ANIMALS 



507. Phylum I. Protozoa.— Vrotozoa, are found in nature 

 practically everywhere where there is moisture; in the soil, in 

 fresh and salt waters and even, as parasites, in the tissues of 

 higher animals and plants. They may even be found in prac- 

 tically dry situations, as in dust, but then only in a resting or 

 spore condition. When Protozoa in this state are moistened 

 they absorb water, the protoplasm swells, the enclosing mem- 

 brane is broken and the organism resumes an active existence. 

 This is why they always appear when a little dry soil, a few dry 

 leaves or any other organic matter is placed in a dish of water. 

 Many species are found the whole world over, others are more 

 limited in distribution. For example, some of the parasitic 

 forms are limited to one, or a few related species of host and 

 consequently are limited to the range of the host. Some groups 

 are peculiar to fresh waters while others are marine. 



508. The number of species of Protozoa is very great and 

 there is great diversity in size, form and habits. Many are 

 easily visible to the unaided eye. Many others approach the 

 limit of visibihty but most can only be seen with the aid of the 

 microscope. The phylum is very difhcult to classify but most 

 forms can readily be placed in one or the other of the following 

 five classes, viz., Rhizopoda, Mastigophora, Sporozoa, Cihata 

 and Suctoria. 



509. Class I. Rhizopoda. — This class is characterized by 

 the temporary root-like processes of the naked protoplasmic 

 body, by which locomotion is effected and food ingested. A 

 common example is amoeba. 



224 



